The presence of increased upper airway resistive loads during sleep can now be diagnosed by paediatricians. However, diagnostic criteria need to be further clarified to allow accurate identification of episodes of partial airway obstruction. New technological advances can be expected to help to determine the clinical usefulness of ambulatory testing during sleep and thus to establish the indications for polysomnographic investigations in the laboratory. A thorough investigation of the anatomical abnormalities that contribute to airways obstruction is essential for selecting the most appropriate therapy. However, the order in which these investigations should be performed remains unclear. The diagnostic tools, including questionnaires and sleep testing, and methods aimed at investigating pathophysiological mechanisms should be standardised for multicentre studies. Familial factors should be taken into account. The best strategy for preventing the complications of the OSA syndrome is to identify the disorder as early as possible. This requires close cooperation between adult physicians and paediatricians called upon to evaluate sleep-related disorders.