The morphologic properties of brain regions co-vary or correlate with each other. Here we investigated the structural covariances of cortical thickness and subcortical volumes in the ageing brain, along with their associations with age and cognition, using cross-sectional data from the UK Biobank ( N = 42,075, aged 45–83 years, 53% female). As the structural covariance should be estimated in a group of participants, all partic...