The cabin filter is underneath the glove box. To find it, move the passenger seat back as far as it will go, and then take out the floor mats. With the seat back, remove the plastic screw and side panel on the left side of the hump near the seat. Next, take out the two 25mm torx screws holding the lower kick panel located beneath the glove box. With the kick panel removed, you can find the cabin filter box. It has a black bottom with 4 torx screws holding it in place. After removal, the filter can be gently pulled down and out and a new one replaced. Perhaps you can see this better described on www.volvospeed.com/repair/s80cfc2.htm (posted last year)