Diminished Chord Quality

Hello David

This is a small point but one I want to check out.

C Major Scale, Second scale degree triad is D F A.  The D scale has two sharps F# C#.  I dont see how the second of that C chord is Dm.  As I understand it Diminshed means that both the 3rd and the 5th would be flattened a half step.  I only see the F as flattened a half step in hte key of D.  

Thanks

gary