Background. Epidemiological data shows the increasing prevalence of chronic rhinosinusitis which poses significant health, social and economic problems in today's world. Endoscopic paranasal sinus surgery is currently the method of choice in the treatment of chronic rhinosinusitis when conservative treatment methods fail. Therefore, maintaining a high percentage of therapeutic success with a constantly growing number of surgical procedures poses the major challenge to otolaryngologists. Appropriate surgical conditions have a great influence on the course of surgical procedure, the risk of complications and postoperative outcomes. Objectives. The aim of this study was to analyse the influence of selected perioperative factors on the course of endoscopic surgery in patients with chronic rhinosinusitis. Material and Methods. A group of 212 patients (105 women and 107 men) aged 19 to 74 (mean age 46.5) diagnosed with chronic rhinosinusitis were enrolled in the retrospective study. All patients underwent endoscopic sinus surgery. The analysis was concerned with the impact of such factors and clinical parameters as gender and age of patients, disease progression, previous (conservative and surgical) treatment, comorbidities, detrimental external factors, the scope of surgical treatment influencing the duration of surgery, bleeding in the surgical field and the total blood loss during surgery. Conclusions. It was found that the mean duration of surgery in the study group was 40.2 min, the mean blood loss was 312.17 mL and the mean degree of intraoperative bleeding scale reached 2.15. The intraoperative conditions deteriorate together with the increasing age of patients. Selected factors and clinical parameters, such as impaired nasal patency, olfactory disorders, the occurrence of nasal polyps, prior surgical treatment, the presence of aspirin-induced asthma and cardiovascular diseases, intranasal glucocorticoid therapy, a high degree of inflammatory changes in the sinuses and a large extent of surgery substantially influence the deterioration in intraoperative conditions. Knowledge of these factors and their impact on surgery enables more thorough, multidisciplinary preparation of patients for surgery, and thus enables the optimisation of surgical conditions (Adv Clin Exp Med 2014, 23, 1, 69-78).