Aryl- and heteroaryl-nitrogen heterocyclic compounds of formula (I): or a pharmaceutically acceptable salt thereof, wherein m, p, q, R1, R2, R3, X1, X2, X3, Y1 and Y2 are defined herein; and compositions containing them, and processes for preparing such compounds. Provided herein also are methods of treating disorders or diseases treatable by inhibition of PDE10, such as obesity, non-insulin dependent diabetes, schizophrenia, Huntington's Disease, bipolar disorder, obsessive-compulsive disorder, and the like.