The study compares the NDVI index with visual assessment of vitality using the Roloff method in species-rich parks. To evaluate the NDVI, a UAV with a multispectral camera has been used in two terms, in early June and in August. In total, 523 trees were analysed in two objects, at the same time with an extensive on-ground survey. The results show a dependency of the NDVI on the vitality classes in the second part of the growing season, significant inter-species variations in the NDVI values, and a difficult prediction of vitality classes.