TD本身不允许出现滚动条，而会总动撑大，所以要想加滚动条需要另外在TD内添加一个容器如:DIV。

例子：

<table style="width: 450px; height: 360px">
<tr>
<td valign="top" style="border:solid 1px gray"><div style="overflow-y:scroll;height:330px;">
<asp:TreeView ID="TreeView1" runat="server" ExpandDepth="1" OnSelectedNodeChanged="TreeView1_SelectedNodeChanged" ShowCheckBoxes="None" ShowLines="true">
</asp:TreeView></div>
                </td>
<td valign="top" style="border:solid 1px gray;"><%--<div style="overflow-y:scroll;height:330px;">--%>
<br />
<asp:Label ID="Label1" runat="server" Text="请选择人员："></asp:Label><br />
<asp:Panel ID="Panel1" runat="server" ScrollBars="Auto" Height="300px">
<asp:RadioButtonList ID="RadioButtonList1" runat="server">
</asp:RadioButtonList>
</asp:Panel>
<%--</div>--%></td>
</tr>
<tr>
<td align="center" colspan="2" valign="top" style="height: 30px">
<input id="Button1" type="button" value="确定" onclick="goback();" /></td>
</tr>
</table>