Salve,
può farlo con javascript così:
Codice HTML:
<script>
function CambiaLista()
{
if(document.getElementById("scegli").value=='Lista1'){document.getElementById("listauno").style.display = 'block';document.getElementById("listadue").style.display = 'none';}
if(document.getElementById("scegli").value=='Lista2'){document.getElementById("listauno").style.display = 'none';document.getElementById("listadue").style.display = 'block';}
if(window.editor){window.editor.refresh();}
}
</script>
<select id="scegli" onchange="CambiaLista()">
<option selected="selected" value="Lista1">Lista 1</option>
<option value="Lista2">Lista 2</option>
</select><br><br>
<select id="listauno">
<option value="Marco">Marco</option>
<option value="Giulia">Giulia</option>
</select>
<select id="listadue" style="display:none;">
<option value="Salvo">Salvo</option>
<option value="Alessia">Alessia</option>
</select>
Cordiali saluti.