As depicted in the film, the real Leonardo Da Vinci kept the Mona Lisa with him all the time until his death.
Danielle's portrait, which Leonardo Da Vinci paints in the film, is actually modeled after another da Vinci work, "La Scapigliata" (also known as "Testa di fanciulla detta la scapigliata").
Mona Lisa is painted on a piece of wood and not on canvas as depicted in the film. This was done intentionally.
King Francois I of France (called Francis in the movie) bought the Mona Lisa for 4000 ecus.