Aim. In this study, we aimed to retrospectively investigate whether pectus excavatum (PE) is a risk factor for the development of primary spontaneous pneumothorax (PSP) and to determine its role in the etiology of the disease. Materials and Methods. Chest-computed tomography (CT) of the patients who were treated for spontaneous pneumothorax between January 2015 and December 2017 in our clinic was examined, and their Haller indices were measured (group I). The patients in the control group who underwent chest CT for other reasons during the same period and were in the same age with the group I were also included in the study (group II) Results. In group I, for patients with PE, the mean Haller index was 2.41, while it was 2.09 in the control group (group II). There was a significant difference between the two groups. Conclusions. PE deformities in the chest wall may predispose to the development of spontaneous pneumothorax, and PE may be among the etiologic factors of spontaneous pneumothorax. Therefore, there is a need for studies involving larger patient groups.