Sažetak The aim of the study was to assess the influence of cognitive abilities on the masticatory system functions in children with cerebral palsy. Forty-three children suffering from cerebral palsy and having different levels of cognitive impairment (aged 6-16 years) were evaluated with regard to their masticatory efficiency using a sieving test. Cognitive abilities were taken from medical documentation of the patients at University Department of Pediatrics, Rijeka University Hospital Center, Rijeka, Croatia. Study subjects were divided into two groups: children with severe and profound mental retardation (group 1) and children with no mental retardation or with mild mental retardation (group 2). There were no subjects with moderate mental retardation. Study results showed that masticatory efficiency values were lower in group 1 including children with severe and profound mental retardation as compared with group 2 that included children with no mental retardation or with mild mental retardation. Comparison of mastication efficiency index in children with cerebral palsy according to the grade of mental retardation yielded a statistically significant difference between the two groups (Z=92.50; p<0.001). It is concluded that the grade of mental retardation plays a major role in the level of masticatory efficiency.