The Cabin Air Filter is located behind the glove box. Open the glove box and note the connecter arm and retainer pin circled below. There is a retainer pin on both sides.

[IMG]C:\Documents and Settings\HP_Administrator\My Documents\My Pictures\RDX Cabin Filter\glovebox release.JPG[/IMG]

Gently unsnap the connecter arm hook from the glove box door by pushing towards the front of the car. Unsnapped it should look like this.