Engaging in physical activity (PA) is crucial for individuals with Parkinson's disease (PD) to maintain functional independence and enhance their quality of life. However, difficulties in measuring PA create challenges when comparing and combining results from various studies, hindering the identification of effective, efficient, and beneficial PA interventions therefore the study aimed to compare the self-reported and objective PA of people with PD in the context of participation in functional physical rehabilitation (FPR). The International Physical Activity Questionnaire and an Actigraph GT3X+ were used to measure the PA. The study included 47 patients with idiopathic PD, aged 64.37±7.12 yrs., disease duration of 6.29 ± 4.02 yrs., in the II and III stages of the disease according to the Hoehn and Yahr scale. The patients were divided into two groups, participating (group A), and not participating (group B) in FPR. The study showed that in both groups, the self-reported level of physical activity was higher than the accelerometer-measured level. However, these differences were not statistically significant in the group participating in FPR. It was concluded that participation in FPR increases the possibility of a reliable assessment of the level of PA.