Hunky movie star Matthew Mcconaughey heaped praise on girlfriend Penelope Cruz during a recent appearance on Oprah Winfrey's US talk show, insisting the Spaniard is "pure on the inside".

The SAHARA star has been dating Cruz for 18 months and insists she never ceases to amaze him, because she has an honesty about her that is completely refreshing.

McConaughey told Oprah, "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... She's very pure on the inside."

And Cruz is helping McConaughey perfect his Spanish.

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