To evaluate the association between cigarette smoking and the frequency of apical periodontitis in female and male patients seeking treatment at the University of Basel (KREBS Project).This cohort study included full-mouth periapical radiographs of 161 subjects, including 66 current smokers, 28 former smokers and 67 [corrected] individuals who had never smoked. The periapical region of all teeth was radiographically evaluated using the Periapical Index (PAI) score. Generalised linear mixed-effects models using the logit link were performed.The frequency of apical periodontitis differed based on gender and smoking status. Current male cigarette smokers with 0.05).Smoking status did not predict apical periodontitis in females and males in this sample group.With respect to quality of root canal filling, tobacco use may not be a significant predictor for apical periodontitis.