diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6c1ffd..8effa8b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,8 +1,10 @@
 # v1.0.8 (pre-release)
 - Added support for AMD GPUs in Linux (Special thanks to @hg000125 for his contribution in #23)
 - Added extra metadata support for chaptered M4B files, ensuring better compatibility with audiobook players.
+- Added new option: `Separate chapters audio format`, allowing to choose between `wav`, `mp4`, `flac` and `opus` formats for chaptered audio files.
 - Skipping PyTorch CUDA installation if GPU is not NVIDIA in WINDOWS_INSTALL.bat script, preventing unnecessary installation of PyTorch.
 - Fixed voice preview player keeps playing silently at the background after preview ends.
+- Fixed not writing separate chapters audio when output is OPUS.
 - Improved input box background color handling, fixed display issues in Linux.
 - Better sleep state handling for Linux.
 - Improvements in documentation and code.
diff --git a/abogen/conversion.py b/abogen/conversion.py
index 779e3e3..823a26b 100644
--- a/abogen/conversion.py
+++ b/abogen/conversion.py
@@ -196,6 +196,9 @@ class ConversionThread(QThread):
                     self.log_updated.emit(
                         f"- Merge chapters at the end: {'Yes' if merge_at_end else 'No'}"
                     )
+                    # Display the separate chapters format if it's set
+                    separate_format = getattr(self, 'separate_chapters_format', 'wav')
+                    self.log_updated.emit(f"- Separate chapters format: {separate_format}")
 
             if self.save_option == "Choose output folder":
                 self.log_updated.emit(
@@ -504,12 +507,14 @@ class ConversionThread(QThread):
 
                     # Concatenate chapter audio and save
                     chapter_audio = self.np.concatenate(chapter_audio_segments)
-                    # Determine chapter extension (.wav for m4b output)
-                    chapter_ext = 'wav' if self.output_format == 'm4b' else self.output_format
+                    
+                    # Use separate_chapters_format
+                    separate_format = getattr(self, 'separate_chapters_format', 'wav')
+                    
                     chapter_out_path = os.path.join(
-                        chapters_out_dir, f"{chapter_filename}.{chapter_ext}"
+                        chapters_out_dir, f"{chapter_filename}.{separate_format}"
                     )
-                    if self.output_format == "opus":
+                    if separate_format == "opus":
                         static_ffmpeg.add_paths()
                         proc = create_process(
                             [
@@ -541,7 +546,7 @@ class ConversionThread(QThread):
                             chapter_out_path,
                             chapter_audio,
                             24000,
-                            format='wav' if self.output_format == 'm4b' else self.output_format,
+                            format=separate_format,
                         )
 
                     # Generate .srt subtitle file for chapter if not Disabled
diff --git a/abogen/gui.py b/abogen/gui.py
index 485cfc7..bde2a88 100644
--- a/abogen/gui.py
+++ b/abogen/gui.py
@@ -23,6 +23,7 @@ from PyQt5.QtWidgets import (
     QCheckBox,
     QMenu,
     QAction,
+    QActionGroup,
 )
 from PyQt5.QtCore import (
     Qt,
@@ -519,6 +520,7 @@ class abogen(QWidget):
             "max_subtitle_words", 50
         )  # Default max words per subtitle
         self.selected_format = self.config.get("selected_format", "wav")
+        self.separate_chapters_format = self.config.get("separate_chapters_format", "wav")  # Format for individual chapter files
         self.use_gpu = self.config.get(
             "use_gpu", True  # Load GPU setting with default True
         )
@@ -1307,6 +1309,8 @@ class abogen(QWidget):
             self.conversion_thread.replace_single_newlines = (
                 self.replace_single_newlines
             )
+            # Pass separate_chapters_format setting
+            self.conversion_thread.separate_chapters_format = self.separate_chapters_format
             # Pass chapter count for EPUB or PDF files
             if self.selected_file_type in ["epub", "pdf"] and hasattr(
                 self, "selected_chapters"
@@ -1620,8 +1624,8 @@ class abogen(QWidget):
                 "Preview Error", "Preview error: No audio generated."
             )
             self.btn_preview.setIcon(self.play_icon)
-            self.btn_preview.setToolTip("Preview selected voice")
             self.btn_preview.setEnabled(True)
+            self.btn_preview.setToolTip("Preview selected voice")
             self.voice_combo.setEnabled(True)
             self.btn_voice_formula_mixer.setEnabled(True)  # Re-enable mixer button
             self.btn_start.setEnabled(True)
@@ -1804,8 +1808,25 @@ class abogen(QWidget):
         max_words_action = QAction("Configure max words per subtitle", self)
         max_words_action.triggered.connect(self.set_max_subtitle_words)
         menu.addAction(max_words_action)
+        
+        # Add separate chapters format option
+        separate_chapters_format_menu = QMenu("Separate chapters audio format", self)
+        separate_chapters_format_menu.setToolTip("Choose the format for individual chapter files")
+        
+        format_group = QActionGroup(self)
+        format_group.setExclusive(True)
+        
+        for format_option in ["wav", "mp3", "flac", "opus"]:
+            format_action = QAction(format_option, self)
+            format_action.setCheckable(True)
+            format_action.setChecked(self.separate_chapters_format == format_option)
+            format_action.triggered.connect(lambda checked, fmt=format_option: self.set_separate_chapters_format(fmt))
+            format_group.addAction(format_action)
+            separate_chapters_format_menu.addAction(format_action)
+            
+        menu.addMenu(separate_chapters_format_menu)
 
-        # Add seperator
+        # Add separator
         menu.addSeparator()
 
         # Add shortcut to desktop (Windows or Linux)
@@ -2295,3 +2316,9 @@ Categories=AudioVideo;Audio;Utility;
                 f"Maximum words per subtitle set to {value}.",
             )
 
+    def set_separate_chapters_format(self, fmt):
+        """Set the format for separate chapters audio files."""
+        self.separate_chapters_format = fmt
+        self.config["separate_chapters_format"] = fmt
+        save_config(self.config)
+