diff --git a/mainwindow.cpp b/mainwindow.cpp
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -65,6 +65,16 @@ MainWindow::MainWindow(QWidget *parent) 
                      SELECT<int>::OVERLOAD_OF(&QButtonGroup::buttonClicked),
                      this, &MainWindow::selectParity);
 
+    // setup data bits selection buttons
+    dataBitsButtons.addButton(ui->rb8Bits, (int) QSerialPort::Data8);
+    dataBitsButtons.addButton(ui->rb7Bits, (int) QSerialPort::Data7);
+    dataBitsButtons.addButton(ui->rb6Bits, (int) QSerialPort::Data6);
+    dataBitsButtons.addButton(ui->rb5Bits, (int) QSerialPort::Data5);
+
+    QObject::connect(&dataBitsButtons,
+                     SELECT<int>::OVERLOAD_OF(&QButtonGroup::buttonClicked),
+                     this, &MainWindow::selectDataBits);
+
     // init port signals
     QObject::connect(&(this->serialPort), SIGNAL(error(QSerialPort::SerialPortError)),
                      this, SLOT(onPortError(QSerialPort::SerialPortError)));
@@ -222,6 +232,18 @@ void MainWindow::selectParity(int parity
     }
 }
 
+void MainWindow::selectDataBits(int dataBits)
+{
+    qDebug() << dataBits;
+    if (serialPort.isOpen())
+    {
+        if(!serialPort.setDataBits((QSerialPort::DataBits) dataBits))
+        {
+            qDebug() << "Set data bits failed: " << serialPort.error();
+        }
+    }
+}
+
 void MainWindow::onPortToggled(bool open)
 {
     ui->pbOpenPort->setChecked(open);
diff --git a/mainwindow.h b/mainwindow.h
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -35,6 +35,7 @@ private:
     Ui::MainWindow *ui;
     QButtonGroup numberFormatButtons;
     QButtonGroup parityButtons;
+    QButtonGroup dataBitsButtons;
 
     QSerialPort serialPort;
 
@@ -59,6 +60,7 @@ private slots:
     void onPortToggled(bool open);
     void selectBaudRate(QString baudRate);
     void selectParity(int parity); // parity must be one of QSerialPort::Parity
+    void selectDataBits(int dataBits); // bits must be one of QSerialPort::DataBits
 
     void onDataReady();
     void onPortError(QSerialPort::SerialPortError error);