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In this paper, we describe a Monte Carlo simulation of the performance of a high-sensitivity and high-resolution small animal positron emission tomography (PET) scanner with a large axial fleld-of-view (AFOV). The simulated camera is based on the photomultiplier-quadrant-sharing (PQS) concept and composed of 180 blocks of 14 times 14 lutetium oxyorthosilicate (LSO) crystals each measuring 1.16 mm transaxially, 1.27 mm transaxially, and 9.4 mm radially. The camera has 84 detector rings with an 11.6 cm AFOV and a ring diameter of 16.6 cm. For the simulation, we used the Geant4 Application for Tomographic Emission (GATE) simulation package. We validated GATE by comparing its predictions for spatial resolution, absolute sensitivity, and count rate with measured data obtained using an existing bismuth germanate (BGO) based dedicated animal PET scanner that had a similar AFOV and ring diameter and was based on the PQS technique. Simulated and experimental images of the Data Spectrum Micro Deluxe phantom were also compared. The simulation data suggested that new LSO-based scanner could have reconstructed radial (tangential) spatial resolutions of 1.14 mm (1.14 mm), 1.31 mm (1.32 mm), 1.54 mm (1.52 mm), 2.01 mm (1.8 mm), and 2.4 mm (2.1 mm) at the center and 1 cm, 2 cm, 3 cm, and 4 cm off center, respectively. The simulation data also suggested that 1.2-mm hot rods in the Micro Deluxe phantom will be distinguishable. Simulation predicted an absolute sensitivity of about 7.3% for a point source at the center of the camera assuming an energy window of 300 keV to 750 keV, a coincidence time window of 8 ns, and a system dead time of 60 ns.