The aim of this study was to investigate potential differences and correlations between brainand skull morphology and the clinical signs of brachycephalic dogs with and without Chiari-likemalformation (CLM). Various measurements were derived from magnetic resonance images ofthe brain and craniocervical junction of thirty brachycephalic dogs in a flexed-neck position.Each dog was assigned a clinical grade. The distance from the planum of the foramen magnum tothe pons was significantly reduced, providing evidence of craniocephalic disproportion similar tohuman patients with Chiari malformation type I. Cerebral length relative to cranial length wassignificantly increased in dogs with CLM compared with control dogs, supporting the hypothesisthat CLM is governed by a global overcrowding of the brain, dissimilar to the human condition.Significant correlations were identified between these measurements and the extent of cerebellarherniation. No significant differences or correlations were identified with clinical grade. This isthe first described morphometric analysis to use a strictly brachycephalic study population inclusiveof a control group free from CLM.