Obstructive sleep apnoea “was defined as the absence of airflow with persistent respiratory effect lasting longer than two baseline breaths, irrespective of arterial oxygen saturation”. Obstructive Apneoa Hypopnoea Index (OAHI) was used to assess the degree of OSA by calculating the total number of obstructive apneas and obstructive hypopnoeas per hour of total sleep time. Of the initial selection, 50 children with OSA (15 were mild with OHAI of 1 to 5 and the remaining severe with an OHAI ≥5) and 27 nonOSA children participated in the study. Neurocognitive function was assessed using the Hong Kong List Learning Test (HKLLT), which assesses learning ability and verbal memory, Trial Making Test (TMT), a tool for the assessment of attention, speed of processing mental flexibility and executive function, Grooved Pegboard Test, which assesses visual-fine motor coordination and the Wechsler’s Intelligence Scale (HK-WISC), used to validate IQ. MRI imaging was perfumed to investigate the global and grey matter volumes. The results revealed the non- OSA group performed significantly better than children with OSA on the TMT and Grooved Pegboard Test. All other neurocognitive tests revealed no significant differences. MRI brain imaging revealed no significant intracerebral abnormalities between the groups. There were however, areas of grey matter deficits were found in the lef and right superior frontal gyri, right supramarginal gyrus, lef lateral occipital gyrus and lef superior temporal gyrus in children with moderate to severe OSA. No significant grey matter change was observed in patients with mild OSA. An interesting correlation was found between the Grooved Pegboard test and the ratio of grey matter to total brain volume. There was a lower the grey matter volume in children who took longer to finish the test and perform poorer. Overall, what was noted in this study was that children with OSA had reduced attention and visual-fine motor coordination compared to non-OSA children and those with more severe OSA were found to have regional grey matter deficits. Childhood OSA might a l t e r a d e v e l o p i n g b r a i n ’ s n e u r o c o g n i t i v e p o t e n t i a l a n d appropriate treatment should be sought.