Objectives Chronic maxillary atelectasis is an infrequent entity and data on its prevalence are lacking. This study investigated the prevalence of chronic maxillary atelectasis and aimed to determine the bilaterality of this entity. Methods The data for 5835 patients who underwent paranasal sinus computed tomography from 2016 to 2020 were retrospectively analysed. Results Fifty-four patients were diagnosed with chronic maxillary atelectasis; its prevalence was 0.92 per cent. The mean age of these 54 patients was 42.98 +/- 18.89 years (range, 18-85 years); 17 of the patients were female and 37 were male. Chronic maxillary atelectasis was unilateral in 42 patients and bilateral in 12 patients (22.2 per cent). Eight patients were found to have enophthalmos with apparent facial asymmetry. Conclusion The prevalence of bilateral chronic maxillary atelectasis may be higher than previously reported and bilaterality may increase as the number of diagnosed cases increases. A unified classification is also proposed, which describes the silent sinus syndrome as chronic maxillary atelectasis IIIS.