So this is a flat ceiling with a floor above? What are the 'moldings' you mentioned - is the molding corner shaped or on the ceiling only or wall only? Any idea what the molding is made of?

Any idea whether this is parallel to the ceiling joists or perpendicular?

How old is the house?

Thanks for the response! Yes flat ceiling with floor above. Mouldin is in the corner, not sure what it is made of... Not sure of the joists either... Is there a way I can tell? Here is a photo that might provide more clarity. Thanks again I really appreciate the help!!

I agree with Lindac92; Its probably a crack over the joint between two sheets of dry-wall. The tape over the joints has split.

The edges of drywall are tapered to form a shallow depression between the sheets. To do a good joint requires 2 to 3 days. First, the joint is taped with one layer of tape and a thin layer of spackling is applied. After this dries, another tape and spackling is applied. The process is repeated until the seam is filled and level with the main wall surface.

Thanks!! I appreciate it. What can I do to patch it?

If it bothers you get a tube of caulk, Dap Quik bathroom caulk red & white tube, cut off tip at angle & squeeze out a little on your finger & rub into the crack, comes in almond or white, or clear(don't like clear)can't tell color of paint but then you can paint over it in couple of days, it doesn't usually reopen, I used it in cracks after a quake at my house & they don't reopen. Just rub it in, don't gob it on crack, crack should be smooth so when painted won't show. I even used it where corners above garage cracked upward, stayed all these yrs. Outdoor caulk I bought once had to redo as it opened up.