Advanced diffusion MRI techniques, such as Neurite Orientation Dispersion and Density Imaging (NODDI), may be used to investigate cortical gray matter (GM) microstructure. In this work, we used the Gray Matter Based Spatial Statistics approach to investigate cortical GM microstructural differences in young people with autism spectrum disorder (ASD). Group differences and age by group interaction models were assessed. We observe regions of reduced neurite density and significant age-related changes of DTI and NODDI metrics in cortical GM of ASD individuals. Findings provide unique evidence of altered neurodevelopmental processes affecting microstructural development in ASD.