<select onchange="stan(this.value)" class="cos_tam" ">
                                  <option value="0" selected  >Wybierz</option>
                                  <option value="dobrze">dobrze</option>
                                  <option value="nie dobrze">nie dobrze</option>
                                  <option value="bardzo zle">bardzo zle</option>
</select>

<select class="cos_tam" id="jest_dobrze" value="0" disabled>
                                  <option value="0" selected >Wybierz</option>
                                  <option value="Nie posiadam">Nie posiadam</option>
                                  <option value="1" >1</option>
                                  <option value="2">2</option>
                                  <option value="3 i więcej">3 i więcej</option>
</select>

function stan(jaki)
{
  
    if ((jaki==0) || (jaki=="dobrze"))
        {
            document.getElementById("jest_dobrze").disabled = 'disabled';
        }
        else
        {
            
            document.getElementById("jest_dobrze").disabled = '';
        }
return;
}

function stan(jaki){
    if ((jaki==0) || (jaki=="dobrze")) {
        document.getElementById("jest_dobrze").disabled = 'disabled';
    } else if ( jaki=='bardzo zle' ) {
        document.getElementById("jest_dobrze").disabled = '';

        var options = document.getElementById('jest_dobrze').getElementsByTagName('option');
        for ( var i = 0; i < options.length; i++ ){
            if ( options[i].getAttribute('value') == 'Nie posiadam' ){
                options[i].disabled = 'disabled';
            } else {
                options[i].disabled = '';
            }
        }
    } else {
        document.getElementById("jest_dobrze").disabled = '';
    }
    return;
}