Cornelis Jan Mension painted landscapes, cityscapes and still lifes. But he became best known with his paintings of small animals such as birds and mice, monkeys and larger wild animals. As a painter he was formed by the lessons of Franz Helfferich in The Hague; then he visited the Academy of Fine Arts in the same city. A free, smooth impressionism is the style that characterized him throughout his life. Mension was also an excellent etcher and lithographer.