I created an enhanced version, based on Trey Copland's fiddle, that I think is more like what you wanted. Added here for future reference to those who come here later. Fiddle example
<body>
<style>
.modal {
height: 390px;
border: 5px solid green;
}
.heading {
padding: 10px;
}
.content {
height: 300px;
overflow:auto;
border: 5px solid red;
}
.scrollable {
height: 1200px;
border: 5px solid yellow;
}
.footer {
height: 2em;
padding: .5em;
}
</style>
<div class="modal">
<div class="heading">
<h4>Heading</h4>
</div>
<div class="content">
<div class="scrollable" >hello</div>
</div>
<div class="footer">
Footer
</div>
</div>
</body>