Objective: The aim of the thesis is to present the epidemiological characteristics of patients treated for spontaneous pneumothorax at the Clinical Hospital Center Split (KBC Split) over a three-year period. Data sources and methods: The study included 115 patients treated for spontaneous pneumothorax at KBC Split between 2021 and 2023. Data were collected through the hospital information system and analyzed using the Shapiro-Wilk test, Mann-Whitney U test, Kruskal-Wallis test, chi-square test, and Spearman's rank correlation coefficient with a significance level of 0.05. Results: The average age of the patients was 53 years, with the majority being male (78.3%). Among comorbidities, COPD was present in 12.2% of patients, lung cancer in 7%, and hypertension in 14.8%. The most common symptoms were dyspnea and pain, with an average length of hospitalization of 6 days. No significant differences were observed among patients regarding the type of surgery or side of pneumothorax, except for a higher rate of rehospitalization in patients with COPD. Longer hospitalization was associated with the presence of a drain or surgery, while dyspnea and COPD were linked to higher pulse rates and lower oxygen saturation. Discussion: The study confirms similar gender trends as previous studies but with different body composition values. The rate of recurrence and percentage of smokers are lower compared to other studies, while there is a higher rate of rehospitalization among patients with COPD. Significant differences in vital parameters were observed in smokers and patients with comorbidities. Conclusions: The study confirmed that spontaneous pneumothorax is more common in men and individuals of average body build, with the most frequent symptoms being dyspnea and pain. Chronic obstructive pulmonary disease (COPD) was identified as the most common comorbidity associated with this condition. Additionally, a significant correlation was found between the length of hospitalization and the duration of drainage in patients with spontaneous pneumothorax.