Background: The neural architecture of executive functions remains a topic of considerable clinical and academic interest in the clinical neurosciences, given its strength as a transdiagnostic predictor of adaptive functioning with high heritability. In recent years, meta-analyses have shown a consistent relationship between prefrontal cortex size and executive functioning task performance in healthy adults and lesion patients, with increases in measures of cortical size (i.e., volume or thickness) associated with better executive functioning performance. There is a gap in meta-analytic literature assessing these relationships in neuropsychiatric populations, their effects relative to healthy controls, and differential contributions of brains regions and neuropsychological paradigms. Methods: We conducted a meta-analysis of published studies ( k =30) that assessed the relationship between executive functions and frontal regions in vivo ( N = 1935) for both healthy (20 samples) and neuropsychiatric (21 samples) adults. Random effects modeling was used to calculate mean effect sizes and CIs. Results: Larger volumes and thickness were associated with better executive functioning in both healthy (r =.35, 95% CI =.29 -.39) and neuropsychiatric populations (r =.47, 95% CI =.40 -.51), with the effect size for neuropsychiatric populations being significantly larger compared to healthy controls. While there was variability between tasks, there were no significant differences in effect size between neuropsychological paradigms or brain region classification. Conclusions: These results indicate the relationship between healthy adult performance on neuropsychological testing is less associated with cortical size compared to neuropsychiatric adults.