Salma Hayek was impressed by Angelina Jolie's "serious" and "professional" sons Maddox and Pax on the set of new movie 'Without Blood'

She told PEOPLE: "They work hard. [Angelina was] very professional with them ... She's demanding. They got the respect of the crew, and they were good with the crew, and they were very in their place. They were not treating me like they treat me outside of there. ... They work hard. They are very serious about what they do."

Salma went on to add: "It is kind of funny, I was teasing them at the beginning, but then I had to say, 'No. I have to separate and just treat them like professionals because it's disrespectful'."

Angelina's sons also worked in the AD department on the set of her movie 'Maria' - which was directed by Pablo Larraín - and she admitted the work is good for them.

She told The Hollywood Reporter: "They've done that quite a few times, and I think that's good for them. Pax tends to do stills and he gets brought in, and Pablo was wonderful and recognised that he was good at it".

The actress was also grateful to have her sons around to support her because playing opera start Maria Callas was so emotionally exhausting.

She added: "It really meant a lot that my boys were with me on 'Maria'. When I would have really heavy times, they would come over and just give me a hug or a cup of tea.

"That was probably one of the more intense things was that - usually when I'm expressing that much pain, it's not in front of my children. You really try to hide from your children how much pain and sadness you carry.

"And so for them to be with you when you're expressing it at such a level, I think it was the first time they ever heard me cry like that. That's usually for the shower."