Chronic maxillary atelectasis (CMA) is characterized by a reduced maxillary sinus volume due to an inward bowing of one or more of the sinus walls. The disorder is probably caused by an obstruction of the maxillary ostium, leading to a persistent negative pressure within the sinus lumen. To provide insight into the epidemiology, pathogenesis and treatment of this disorder, a retrospective study of twelve cases that met radiographic criteria of CMA was carried out. The patients were equally divided between both sexes and were on average 25 years old. Five of the twelve patients were under eighteen years of age. The patients had chronic sinonasal complaints except two, who had a "silent sinus syndrome", characterized by enophthalmos associated with a marked sinus deformation. This is the first report of CMA associated with a benign nasal tumour and also of CMA following cicatrisation due to nasal packing for bleeding after endoscopic sinus surgery. All patients were treated surgically by creating a middle meatal antrostomy, thus restoring sinus ventilation. To conclude, CMA is rare and probably underestimated, especially in the paediatric population. Different entities causing a complete ostial occlusion can lead to CMA. Endoscopically restoring maxillary sinus ventilation is the recommended treatment.