Obstructive sleep apnoea (OSA) is a serious worldwide health problem. Moderate-to-severe OSA has been found in up to 50% of men and 25% of women in the middle-aged population. It results in a fourfold increase in all causes of mortality. The prevalence of OSA is underestimated, partly due to absence of symptoms but also lack of knowledge amongst the population at large as well as sectors of the medical profession. Imaging, performed predominantly by clinicians and research scientists, has been integral to evaluating the anatomical basis of OSA. Increased nasal resistance and a narrowed and elongated oropharynx lead to increased collapsibility of the upper airway, predisposing to airway collapse and apnoea during sleep when there is reduction in tone of the pharyngeal dilator muscles. Unfortunately, a significantly narrowed upper airway is usually ignored by radiologists: it is not part of their reporting ‘check-list’. The imaging findings in the upper airway that are strongly associated with OSA and its sequelae in various organ systems are discussed. Imaging can strongly suggest OSA; the diagnosis requires a polysomnogram for confirmation. Treatment of moderate-to-severe disease is primarily with positive airway pressure applied by a nasal or oral mask which splints the upper airway. Although highly effective, compliance is limited and other treatment modalities are increasingly being utilized.