This study determined the canal flare index (CFI) of four dog breeds using two distinct femoral regions as a reference. Thirty-five radiographs of the hip joints of Golden Retrievers (GRG), German Shepherds (GSG), Labrador Retrievers (LRG), and Rottweilers (RG) of both sexes were used. Seventy experimental units were submitted to CFI calculation. Objective (CFIob) and subjective (CFIsub) values of the CFI of each experimental unit were determined according to the anatomical reference used for the calculation. A significant difference in the CFIob between the Golden Retriever and German Shepherd breeds (1.68 ± 0.16 and 1.49 ± 0.08), and in the CFIsub between Golden Retriever, German Shepherd, and Rottweiler breeds (2.09 ± 0.31, 1.86 ± 0.11, and 1.84 ± 0.18) was reported. The subjective form of measurement showed higher values than the objective form (GRG: 2.09 ± 0.31; GSG: 1.86 ± 0.11; LRG: 2.07 ± 0.12; RG: 1.84 ± 0.18). The CFI values of each breed were similar, suggesting a certain racial pattern. A significant difference in the interobserver assessment for both CFIsub and CFIob, in all races was observed. The CFI analysis identified morphological patterns of the proximal femur in the different races. Results indicated the need for standardization of the anatomical references used to calculate the CFI because there were statistical differences among the measurements among the observers.