It is well known that in ad hoc networks the interference at a given receiver is expressed by the sum of several random variables representing the distinct sources of interference, and no exact closed-form distribution is known for such a sum. This work characterizes the interference distribution of a Cognitive Radio ad hoc Network (CRAHN) based on Code Division Multiple Access (CDMA). The authors start to explore an analytical model for the multiple-access interference of a Primary User (PU), being thereafter extended to embrace the co-existence of a Secondary User (SU) network. Several scenarios are simulated and the results are compared to the proposed analytical model.