 <p>What you say doesn't seem to match with the c3p0 docs. Namely it seems there is only a subset of c3p0 parameters that can be accessed through hibernate.cfg.xml. Everything else must be set through a separate c3p0.properties file. See <a href="http://www.mchange.com/projects/c3p0/index.html#hibernate-specific" rel="nofollow">http://www.mchange.com/projects/c3p0/index.html#hibernate-specific</a></p> <p><strong>Edit: It seems the c3p0 docs are completely wrong.</strong> If you do as they say (e.g. include an additional c3p0.properties file) it will be ignored. However, if you simply add the properties to the hibernate config file in the same fashion, it works fine. E.g. adding the following to hibernate.cfg.xml worked, where the prescribed method did not:</p> <pre><code>&lt;property name="hibernate.c3p0.acquireRetryAttempts"&gt;100&lt;/property&gt; &lt;property name="hibernate.c3p0.debugUnreturnedConnectionStackTraces"&gt;true&lt;/property&gt; &lt;property name="hibernate.c3p0.unreturnedConnectionTimeout"&gt;120&lt;/property&gt; &lt;property name="hibernate.c3p0.checkoutTimeout"&gt;30000&lt;/property&gt; </code></pre> <p>There's 2 hours of my life i won't get back. :-(</p>