How long after Q-switch do you have to wait to do CO2 fractional laser?

The issue with using multiple devices simultaneously, or spaced shortly apart, is the total amount of energy delivered. I very commonly use these lasers and more in combination, simultaneously, for resurfacing,  tattoo removal, etc. to achieve the best result that we can with each. The safety of this is well described in our literature. 
You will just want to make sure that your physician has the appropriate training, comfort level, and has planned appropriately.
To ensure you are receiving the highest level of care, seek out a modernly trained, new-school dermatologic surgeon, oculoplastic surgeon, facial plastic surgeon or plastic surgeon who is board certified and fellowship trained in one of these "core four" cosmetic specialties.
Cameron Chesnut#realself500 Physician

Thank you for your question ElyD.
Fractional CO2 laser resurfacing is an
outstanding treatment that can address multiple aspects of aging in a single
treatment. Q-switched lasers are used for tattoo removal as well as color correction for concerns such as melasma. When having any laser treatment, there is some inflammation in the skin which takes some time to resolve. I either perform multiple treatments on the same day (so there is inflammation once) or wait one to two weeks between treatments (and longer for ablative treatments) so that we do not treat skin that is still healing from inflammation. This typically yields the best results and recovery. Please consult with a doctor for
specific recommendations. Good luck!

My suggestion would be to wait at least 2 weeks but even 4 weeks between any laser procedure. You wouldn't want to create to much heat on a recently treated area and possible cause a permanent scar.