 <p>Use the <a href="http://msdn.microsoft.com/en-us/library/system.linq.enumerable.selectmany(v=VS.90).aspx" rel="nofollow noreferrer"><code>SelectMany</code></a> extension method:</p> <pre><code>List&lt;List&lt;int&gt;&gt; lists = new List&lt;List&lt;int&gt;&gt;() { new List&lt;int&gt;(){1, 2}, new List&lt;int&gt;(){3, 4} }; var result = lists.SelectMany(x =&gt; x); // results in 1, 2, 3, 4 </code></pre> <p>Or, for your specific case:</p> <pre><code>var performancePanels = new { Panels = (from panel in doc.Elements("PerformancePanel") select new { LegalTextIds = (from legalText in panel.Elements("LegalText").Elements("Line") select new List&lt;int&gt;() { (int)legalText.Attribute("id") }).SelectMany(x =&gt; x) }).ToList() }; </code></pre>