Purpose: The aim of this study was at evaluating the effects of long-term cannabis use on the corneal endothelial cells with the specular microscopy.Methods: The study enrolled 28 eyes of 28 patients diagnosed with cannabinoid use disorder. The cannabinoid group was selected among patients who had been using the substance for three days or more per week over the past one year. Thirty-two eyes of 32 age- and sex-matched healthy individuals enrolled as control group in the study. Corneal endothelial cell density (CD), coefficient of variation (CV) and hexagonal cell ratio (HEX) values were analyzed by specular microscopy.Results: The mean CD was 2900211 cells/mm(2) in the cannabinoid group and 3097 +/- 214 cells/mm(2) in the control group (p<0.01). There was a significant decrease in cannabinoid group. The mean CV was 29 +/- 7 and 27 +/- 4 in the cannabinoid and control groups, respectively (p>0.05). No significant difference was present between the cannabinoid and the control groups in terms of mean CV value. The mean HEX was 52 +/- 5% in the cannabinoid group and 53 +/- 10% in the control group (p>0.05). There was not a significant difference between the cannabinoid and the control groups in terms of mean HEX value.Conclusion: A significant decrease in CD was found in cannabinoid users compared the control group.