You could install moulding to cover it up. It all depends on the gap. If it is wide then the moulding is the way to go. If small, you can put a gasket in, then top with paintable caulk or drywall patch and then paint. If you paint, use a primer first before your second coat of paint.
Is it Drywall? Not really a common problem. Do you have a picture?
What is causing the gaps? Are they just there or do they show up every so often? A photo would help.
You can use crown molding. Something to consider?
Hi. I hope this is just plaster or paint separating. If it's big, get a contractor in to see what's going on. For a small crack, paintable bathroom/kitchen caulk will do the trick. Happy DIY'ing!
Hi Carol, it could be seasonal separation. This has happened in all of our houses. In the winter a gap appears, and in the summer, when the molding swells with the increased temperature, they go away. Did you notice the gaps in the summer?