InputDialog dlg = new InputDialog(Display.getCurrent().getActiveShell(), "Test", "Please input text.",
            "Test-Text", null) {

          /**
           * Override this method to make the text field multilined
           * and give it a scroll bar. But...
           */
          @Override
          protected int getInputTextStyle() {
            return SWT.MULTI | SWT.BORDER | SWT.V_SCROLL;
          }

          /**
           * ...it still is just one line high.
           * This hack is not very nice, but at least it gets the job done... ;o)
           */
          @Override
          protected Control createDialogArea(Composite parent) {
            Control res = super.createDialogArea(parent);
            ((GridData) this.getText().getLayoutData()).heightHint = 100;
            return res;
          }
        };
        dlg.open();