Matthew McConaughey has praised girlfriend Penelope Cruz for her purity.

The film star, who has been dating Cruz for 18 months, told Oprah Winfrey on The Oprah Winfrey Show that she is "pure on the inside."

He added: "She sees everything for the first time even if she's already seen it before. That's refreshing…She takes nothing for granted. She doesn't come in with a library of what she expects even though she may have been there before."

McConaughey also said that the star of Captain Corelli's Mandolin is assisting him with his Spanish.

"She laughs at what I'm saying a lot of the time," he explained, "but put me in Mexico or you put me in Spain (and) I can get what we need."