The tree of heaven (Ailanthus glandulosa or Ailanthus altissima) was brought to Europe from northern China in the mid-18-th century, and since then this species has continued spreading. This plant has low habitat and climatic requirements and it also shows an astonishing ability to absorb gas air pollutants and restore oxygen concentration. It is thus an extremely valuable plant for urban and industrial areas and it should also be promoted for its decorative values.