Our group has conducted a series of studies on behavioural, biomarker, and neuropsychological research in neurodevelopmental disorders, including autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) in children. Our findings highlight the psychiatric and physical comorbidities that are highly prevalent among children with neurodevelopmental disorders. We have also validated various instruments that have been used for assessing autism and ADHD in western countries. The Chinese versions of these instruments are now being widely used in Hong Kong. Recently, we have embarked on the study of the psychopathology and cognitive and functional impairments in young adults with a previous clinical diagnosis of ADHD in childhood. Another vein of aetiological exploration into the microbiome signature of ASD is underway to elucidate the pathomechanism at gut-brain interface that may offer an avenue for early detection and early intervention. A double-blind randomized controlled trial on the effectiveness, tolerability and feasibility of transcranial direct current stimulation is underway for pre-pubertal ASD children with comorbid ADHD.