yo,
while ($row_thema = mysql_fetch_array($result_thema))
{
if ($row_thema[ID] == alter_formularwert)
echo "<option value='$row_thema[ID]' selected>$row_thema[Thema]
else
echo "<option value='$row_thema[ID]'>$row_thema[Thema]
</option>";
}
Ilja