Hollow cheeks. What filler to use? Can it be done?

All fillers can be used to add volume to the cheek.  The HA fillers are wonderful to give volume.  You will see the results immediately.  The issue with Perlane, Restylane, and Juvederm is these fillers last 6-9 months, and you will likely require multiple syringes, making maintenance of this more costly.

For large volume needs (in general hollow cheeks would fall into this) I would recommend sculptra.  It is better for large volumes and lasts for 2 years.   It is more of a process, requiring 2-3 rounds of injections spaced 6 weeks apart, and it grows slowly, so the results are not immediately seen.  But for large volumes, I feel it is more cost and time effective.

Please see the other blogs on Sculptra.  I have to say I am a fan of its subtle natural results.