The Scream stars separated in 2010, but they regularly meet up to take little Coco on days out - and Cox admits it feels like "a big deal" if they go more than a week without seeing each other.
The actress is convinced the split has improved their parenting capabilities to their seven-year-old daughter, as they are able to talk through their issues more easily now they lead different lives.
Cox tells Britain's Stella magazine, "We weren't really dealing with what needed to be dealt with, which was how to stay married and be true intimate partners.
"Now we're separate we're able to talk about all our resentments and the things we should have listened to each other on. We kind of know where it went wrong, and how we felt ourselves drifting apart. So now we have this really great, open relationship. We speak to each other all the time; if we don't see each other in a week it's a big deal.
"And we're better parents to Coco. We're more patient with each other."
The actress also opens up about how the stars parent their daughter, adding: "I'm probably not as good a disciplinarian as David, but I relate to her emotions. Mind you, I'm frightened of the teen years. Coco's got a very strong will, and I'm a little afraid of that."