The collection contains Old Masters as well as Impressionist, Cubist, and Expressionist paintings, drawings and prints by artists including Claude Monet, Pierre-Auguste Renoir, Paul Cézanne, Paul Gauguin, Henri Matisse, Eugène Delacroix, Edgar Degas, Henri de Toulouse-Lautrec, Franz Marc, Marc Chagall, Édouard Manet, Camille Pissarro, Auguste Rodin, Otto Dix, Edvard Munch, Gustave Courbet, Max Liebermann, Wassily Kandinsky, and Paul Klee, among many others, as well as works by family members who were themselves artists. A considerable portion of the collection is in the form of prints and other "dealer stock" in addition to a smaller, but still noteworthy number of unique and more valuable works; initial sensationalist claims of the value of the collection being "in excess of 1 billion dollars" based on its size alone have proved to be unfounded, though the collection is certainly worth tens of millions of dollars. Legally, Cornelius was the owner of all the works upon their discovery, because in Germany, legal claims on potential looted works expire after 30 years; however, from 2012 he agreed to voluntarily return any works that were shown to be looted to the heirs of the families concerned, a provision that has been carried on by the new custodians of the collection. To date, six pieces have been returned, being works by Henri Matisse, Max Liebermann, Carl Spitzweg, Camille Pissarro, Adolph von Menzel and Paul Signac, while a profit-sharing agreement was reached with the heir of another family for a work by Max Beckmann prior to its sale in 2011.
