The actor said she didn’t feel as if she was acting when she played Minerva McGonagall in the wizarding films, or in her role as Violet Crawley in the period drama.
Discussing her work in the earlier years of her career, Dame Maggie told ES magazine: “It seemed to take ages to get away from light comedy.
“I am deeply grateful for the work in [Harry] Potter and indeed Downton [Abbey] but it wasn’t what you’d call satisfying.
“I didn’t really feel I was acting in those things.”
Dame Maggie is known for film and TV roles and also returned to the stage this year in A German Life, in which she is the only star.
She said as soon as she agreed to do the play she suffered “doubt, doubt, doubt”.
“I suddenly felt twice as old as I actually was,” she said.
“And also, when you haven’t done a show for a long time, there’s something pretty dumb about doing it totally on your own.”
Earlier this year, the 84-year-old reprised her Downton Abbey role for its first outing on the big screen.
After it proved to be a critical and commercial success, one of the film’s producers, Graham Neame, has confirmed there is a potential sequel in the works.
He told The Hollywood Reporter last month: “We’re working on what the story is, and when we might be able to make it.
“But it’s the same as the first time around: we have to try and get everyone back together again. And that was very challenging.”
The full interview with Dame Maggie Smith appears in this week’s issue of ES magazine, out Thursday.