[LucianoRey]

Hola, no he usado jakarta poi, pero el ejemplo que trae para mezcla de celdas es esta:

    HSSFWorkbook wb = new HSSFWorkbook();
    HSSFSheet sheet = wb.createSheet("new sheet");
    HSSFRow row = sheet.createRow((short) 1);
    HSSFCell cell = row.createCell((short) 1);
    cell.setCellValue("This is a test of merging");
    sheet.addMergedRegion(new Region(1,(short)1,1,(short)2));
    // Write the output to a file
    FileOutputStream fileOut = new FileOutputStream("workbook.xls");
    wb.write(fileOut);
    fileOut.close();

, espero te sirva, saludos.