In this paper, we present a model to simulate accurately two main performance parameters of Single-Photon Avalanche Diodes (SPAD) in Complementary Metal-Oxide Semiconductor (CMOS) technology, the Photon-Detection-Probabilty (PDP) and the Dark-Count-Rate (DCR). The model development has been driven by the necessity to comply with the specifications of SPAD used for future space LIDAR applications. To evaluate these statistical parameters, the model is based on a combination of measurements to acquire data related to trap population, Technology CAD (TCAD) simulations and a Matlab routine.