Obstructive sleep apnoea (OSA) in children is a prevalent sleep disorder associated with a wide spectrum of morbidities, including neurobehavioural, cardiovascular, and metabolic complications. Positional OSA (POSA) is one of the distinct clinical phenotypes in which obstructive respiratory events occur predominantly while sleeping in the supine position. As the majority of the OSA events in POSA occur in the supine position, positional therapy has become a reasonable non-invasive treatment strategy. The primary objectives of our study are 1) To investigate the feasibility of positional therapy in children with positional OSA; 2) To investigate the efficacy of positional therapy in children with positional OSA. Hypothesis to be tested: 1) Positional therapy is feasible in children with positional OSA. 2\) Positional therapy is efficacious in children with positional OSA by improving sleep related symptoms and quality of life. Design and subjects: A prospective case-control study. 20 children aged 6 to 17 years of age with positional OSA (POSA) will be invited to join the study. Primary and secondary outcome measures: The changes in sleep-related symptoms, quality of life and behavioral measures between the baseline and 3 months after treatment with a positional device therapy. Adherence to the positional device. Statistical Analysis: Continuous data will be presented as mean and standard deviation or median with the interquartile range depending on its distribution, whereas categorical data will be shown as proportions. Changes in outcome measures between the baseline and 3 months after using the positional device will be compared using Wilcoxon signed rank tests. Within-subject differences in the outcome parameters will be tested by paired t-tests, McNemar tests, and marginal homogeneity tests for continuous, dichotomous, and categorical data respectively. Expected results: Positional therapy is practicable and efficacious in children with positional OSA by improving sleep related symptoms.