The sport has today been marking the 20th anniversary of Senna's death, who passed away at the age of 34 following a crash in the San Marino Grand Prix.
"Ayrton was reasonably complicated," BBC Sport quotes Ecclestone as saying. "I always thought that he had a bit of a conflict going on inside with all sorts of things.
"Obviously his results speak for themselves - the world knows that. As a friend, he was super - somebody I could trust. He was very close to my family. He was a nice guy."
A memorial service for the sportsman was held in Imola today.