There are considerable differences in cognition between individuals with Parkinson's Disease (PD) which might be explained by the theory of cognitive reserve. This theory states that premorbid factors, such as high intellectual capacities, provide a buffer against cognitive impairments. This study determines whether cognitive reserve influences cognition in PD. Forty-eight PD patients were included. All were assessed with two proxies of cognitive reserve, tests of cognition and both measures of disease characteristic and symptoms of depression. After accounting for age, gender, disease characteristics and depression, cognitive reserve was an independent predictor of cognitive performance. In conclusion, cognitive reserve influences cognition in PD, i.e. PD patients with a high premorbid intellectual ability show fewer cognitive impairments than patients with a low premorbid ability. This indicates that cognitive reserve needs to be taken into account when monitoring the evolution of cognition in PD, however, verification of results on a larger patient sample would be desirable.