Various studies have reported deficits in frontal cognitive functions in patients with multiple sclerosis (MS). However, the frontal deficit is not uniform and is often very subtle. The aim of this study was to assess frontal functions in a broad sample of patients with relapsing–remitting multiple sclerosis at the mild-to-moderate stage. The sample included a series of 165 patients. We used a test battery covering the frontal functions that have been described as being altered in MS. Significant differences were found between the patient group and healthy controls on the WAIS Arithmetic subtest, the PASAT, category word recall and the number of trials required to reach the first category of the WCST. In conclusion, we observed significant differences with respect to the control group in terms of information processing speed and working memory. These functions involve connections between the frontal lobe and other brain regions.