Obstructive sleep apnea syndrome in children is a manifestation of sleep-disordered breathing and associated with a number of complications. Structural narrowing of the upper airway in combination with inadequate compensation for a decrease in neuromuscular tone is an important factor in the pathogenesis. Adenotonsillar hypertrophy is the most important predisposing factor. However, many other causes of craniofacial defects may coexist. Additionally, the pathogenesis of narrowing is more complex in certain subgroups such as children with obesity, craniofacial malformations, Down syndrome or neuromuscular disorders. The diagnosis of obstructive sleep apnea is based on an overnight polysomnography. This investigation is expensive, time consuming and not widely available. In view of the major role of structural narrowing, upper airway imaging could be a useful tool for investigating obstructive sleep apnea and in establishing the site(s) of obstruction. Several radiological techniques (lateral neck radiography, cephalometry, computerized tomography, magnetic resonance imaging and post-processing of these images using computational fluid dynamics) have been used to investigate the role of structural alterations in the pathogenesis. We reviewed the literature to examine if upper airway imaging could replace polysomnography in making the diagnosis and if imaging could predict the effect of treatment with a focus on adenotonsillectomy. There is a limited number of high quality studies of imaging predicting the effect of treatment. To avoid unnecessary risks and ineffective surgeries, it seems crucial to couple the exact individual anatomical risk factor with the most appropriate treatment. We conclude that imaging could be a non-invasive tool that could assist in selection of treatment.