This study evaluated the effects of rehabilitation of existing coal mining spoils on species composition and species diversity. The species composition of most rehabilitated stands differed from that of the reference stands, and thus did not suggest successful rehabilitation. However, stands subjected to restorative treatment many years ago showed higher species diversity than the reference stands and thereby met the goals of rehabilitation. Our results demonstrate that restorative treatments practiced in the past created a heterogeneous ecological space with regard to the surrounding areas. Therefore, even though species diversity increased several years after rehabilitation, this does not indicate that the treatment achieved true rehabilitation success. The treatment did result in temporary stability through increased species diversity, but it could not be described as successful rehabilitation in terms of biological integrity with the surrounding ecosystems.