Objectives: Epidemiological studies show that apical periodontitis (AP), alongside tooth decay, is the most common oral disease. The aim of the study was to evaluate the influence of smoking on the prevalence of AP in the population of the Łódź region, Poland. Material and Methods: The study involved 815 first-time, randomly selected patients reporting to the Central Teaching Hospital of the Medical University of Lodz. The studied group was a systematic sample of the population admitted for treatment in 2016. The study consisted of a questionnaire and a radiological part. Each patient filled out a questionnaire containing demographic data, and an interview regarding smoking and diabetes. The radiological part of the study included the analysis of panoramic radiographs which showed the periapical status, and the presence and quality of root canal treatment. Results: Teeth with AP were observed more frequently in patients addicted to tobacco either at the time of the study or in the past (group 1) – 7.2% than in people who had never smoked (group 2) – 5.2% (p < 0.0005). In the teeth without root canal treatment, AP was observed more frequently in group 1 – 3.5% than in group 2 – 1.9% (p < 0.0005). A statistically significant difference was found in the percentage of endodontically treated teeth between group 1 and group 2 (10.7% vs. 9.6%) (p = 0.017). However, no difference was observed in the frequency of AP in the endodontically treated teeth in both groups (37.6% vs. 35.8%) (p = 0.451). Conclusions: Smokers are a group facing an increased risk of AP and, therefore, there is a need for an early detection and treatment of caries and its complications in this group of patients. The multifactorial etiology of AP indicates the necessity to undertake further studies on the effect of smoking on the periapical status. Int J Occup Med Environ Health. 2020;33(1):45–57