Background. Given increases in cannabis potency and cannabis use in newly legalized markets, it remains critical to examine the effects of cannabis on a variety of health outcomes. However, quantification of cannabinoid exposure remains rare in cannabis research. It is unclear whether biospecimen measures of cannabinoid exposure, such as those derived from hair, are associated with common self-report measures of use and cognitive and mental health outcomes. Methods. 74 near-daily cannabis users with cannabis use disorder self-reported their quantity of cannabis use, cannabis use-related problems, estimated cannabis potency, and mental health outcomes, and completed cognitive tests. Hair samples were provided to quantify Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD), and cannabinol (CBN) using a liquid chromatography atmospheric pressure chemical ionization-tandem mass spectrometry method. Results. Cannabinoids were detectable in 95.95% of the hair samples from individuals who tested positive on a urine screen for cannabis. Hair-derived Δ9-THC concentrations were positively associated with several measures of self-reported potency (relative potency, potency category, and perceived ‘high’) although Δ9-THC, CBD, or CBN concentrations or THC/CBD ratio were not associated with self-reported quantity of use. Furthermore, self-reported THC percentage (category) and potency (category), but not cannabinoid concentrations, were associated with withdrawal and craving respectively. Self-reported measures of quantity of cannabis use (gram/week), but not cannabinoid concentrations, were associated with cannabis use related problems. Mental health problems were associated with self-reported cannabis use-related problems and withdrawal only. Looking at cognitive outcomes, only a small negative association between a measure of cannabis use related problems and estimated IQ was observed. Conclusions. The use of hair-derived cannabinoid quantification is supported for detecting cannabis use in near-daily users. However, the general lack of associations between hair-derived cannabinoid concentrations and commonly used self-report measures does not support the use of hair analyses for quantifying cumulative cannabinoid exposure at this time. Further research comparing hair-derived cannabinoid concentrations with other biological matrices (e.g. plasma) and self-report is necessary to further evaluate the validity of hair analyses for this purpose. The importance of accurately quantifying cannabinoid exposure in research into the effects of cannabis cannot be overstated given newly permissive legal environments and uptick in use.