In 2018, California legalized the sale of cannabis for adult non-medical use. To understand use of cannabis after legalization, we surveyed a stratified random sample of adults in a large health system (aged 19-64) with and without documented chronic pain (CP) about their reasons for cannabis use from November 2018 to March 2019. We compared patients with and without CP on measures for medical, non-medical, pain-related, and mental health-related cannabis use based on self-reported symptoms. Patients with CP reported higher past year medical use (34.6%) compared to patients without CP (22.8%), past year pain-related use (29.7% vs 15.5%), and past year mental health-related use (24.8% vs 18.9%). In adjusted models, relative to patients without CP, those with CP had a 6.2% (95% CI: 0.010-0.11) higher probability of past year medical cannabis use and an 8.0% (95% CI: 0.035-0.13) higher probability of past year pain-related cannabis use. Compared to patients without CP, patients with CP were more likely to use cannabis for reasons related to medical and pain symptoms in the past year. Use for past year mental health symptoms did not differ between these two groups. Cannabis use among patients with and without CP is common after legalization for non-medical use and understanding reasons for use is important to improve overall patient care.