The frontal sinus (FS) as a component of the system of the paranasal sinuses performs phonetic, olfactory, static, thermal insulating, and protective functions. Patients and methods. Four patient groups: 1) acute and chronic inflammatory lesions in FS (n=480); 2) recurrent frontitis (n=11), 3) cystoid stretching (n=25); 4) traumatic lesions (n=24) were followed up in 2007—2012. Results. Analysis of the data of the patients’ medical history and nasal cavity computed tomography and endoscopic examination could identify subgroups of patients with acute and chronic sinusitis according to the method of performed treatment. Forty-two patients received antibiotic therapy. LS trephination and antibiotic therapy were performed in 336 cases; drainage and endoscopic endonasal surgery were made in 47; 46 patients were treated only endoscopically. Extranasal FS dissection in combination with endoscopic one was performed only in 9 patients. All the patients with FS cystoid stretching underwent endonasal endoscopic surgery. Bone fragments were repositioned and the sinus shape was restored in the patients with traumatic lesions in FS.