The diet of Pleistocene cave bears (Ursus spelaeus, U. deningeri) is debated extensively. Traditionally, cave bears were thought to be herbivorous, but more recent studies have proposed that they were more omnivorous. To test this, their skull morphology and that of their confamilials were analysed using 3D geometric morphometrics. The eight extant Ursidae occupy various dietary niches, which are expected to affect the functional morphology of the skull; the resulting dietary morphospace is used to determine the position of cave bears. Landmarks for 3D digitisation were chosen to reflect functional morphology. Extant and extinct Ursidae were digitised with a Microscribe G2. Generalised Procrustes superimposition was performed on the raw coordinates and allometry removed by regressing these onto the log (ln) centroid size pooled per species. Principal component analyses (PCA) and two-block partial least squares analyses (2B-PLS) were conducted on the regression residuals, and (multivariate) analyses of (co)variance ((M)AN(C)OVA) and discriminant function analyses (DFA) performed on the PC scores. PCA and 2B-PLS differentiate between known dietary niches in extant Ursidae. (M)AN(C)OVA and DFA results suggest that cave bears were herbivorous. Differences in the results between the temporalis and the masseter are seen primarily in the position in morphospace of the extant spectacled bear (Tremarctos ornatus), probably due to the influence of its premasseteric fossa on the morphology of the masseteric fossa. Additionally, ANOVAs suggest that there was intraspecific variation within U. spelaeus contradicting lineages proposed on the basis of mitochondrial DNA. This variation may be attributable to environmental factors, such as timberline altitude, influencing the cave bears’ diet.