While living in Greenwich Village, Mentis made his living by painting portraits on the weekends in Washington Square in New York. He continued to excel in portrait painting and later exhibited at The Boston Museum of Art, The Sal Magundi Club, The Kent Arts Association, The Scott Fanton Museum, The Yale Art Association and many more. He won many first place prizes at the exhibitions while continuing to paint portraits from life. Mentis paints with various mediums including oils, watercolors, pastels, and he even does sculpture with Italian clay. He is listed in Who’s Who in American Art.