Fabio Cavallucci, director of the Center for Contemporary Art, which oversaw the installation, said, "There is no intention from the side of the artist or the center to insult Jewish memory."
"It's an artwork that tries to speak about the situation of hidden evil everywhere," he said.
The Hitler installation is just one object in a retrospective of Cattelan's work titled "Amen," a show that explores life, death, good and evil. The other works are on display at the center itself, which is housed in the Ujazdowski Castle.
The Hitler representation is visible from a hole in a wooden gate across town on Prozna Street. Viewers only see the back of the small figure praying in a courtyard. Because of its small size, it appears to be a harmless schoolboy.
"Every criminal was once a tender, innocent and defenseless child," the center said in a commentary on the work.
Poland's chief rabbi, Michael Schudrich, said he was consulted on the installation's placement ahead of time and did not oppose it because he saw value in the artist's attempt to try to raise moral questions by provoking viewers.