We are currently developing a multi-layer APD based detector for use in PET that utilizes thin continuous crystals. In this work we developed a Monte-Carlo based simulation to aid in the design of such detectors. We measured the performance of a detector comprising a single thin continuous crystal (3.1mm x 9.5mm x 9.5mm) of LYSO and an APD array (4 x 4) elements; each element 1.6mm sq. and on a 2.3mm pitch. We showed that a spatial resolution of better than 2mm is achievable throughout the crystal provided we adopt a ‘Statistics Based Positioning’ (SBP) Algorithm. We then used Monte Carlo Simulation to model the behavior of the detector. The accuracy of the Monte-Carlo simulation was verified by comparing measured and simulated parent datasets (PDS) for the SBP algorithm. These datasets consisted of data for point sources at 49 positions uniformly distributed over the detector. We show that the performance of the simulation closely matches the measured performance. In summary, we have developed a model that can be used to simulate the performance of a variety of APD based PET detectors.