Query is slow for certain users I have a couple queries called from a C# .NET web application which are always fast for me (I am an local admin on the SQL Server) but for a group of users (domain group with required permissions), the query is incredibly slow to the point it times out in the application. 

What would cause the exact same query to run differently for different users?

More info:


The query is inline SQL in the C# code, not a stored procedure
The app uses domain authentication and both the user and myself run the query through the app
Seems like the issue is different plans and one was cached so that is why it was different for different users. Something is affecting the cache because now the query is slow for me via the app and fast in SQL Server Management Studio.
If the parameters are the same (I'm assuming that's what's meant by exact same query), it shouldn't be parameter sniffing (users get a bad plan for the wrong parameter(s)), but rather users are getting different plans for the same parameter(s). It could be because of settings like quoted_identifier and arithabort, which you can compare in sys.dm_exec_sessions for the fast user and the slow user, or it could be because they have different default schemas and objects are referenced without the schema prefix. Parameter sniffing may still be involved (hence why one of them has a bad plan).