This document describes the development of a finite element model of the Q3 three year old anthropomorphic test device (ATD) in LS-DYNA. The model, which consists of 49,664 elements, includes all materials and structural details of the Q3 dummy. It was developed by means of non-destructive reverse engineering which included digitizing, x-rays and a CAT-scan of the whole dummy. The materials were calibrated with component level tests and through an optimization analysis. The component tests included head drop, lateral and frontal neck pendulum, lateral and frontal lumbar spine pendulum, ribcage compression, and abdomen compression tests. The optimization process has yielded satisfactory component responses within the range of the specific materials and the functionality of the finite element analysis software. Assembly level tests were used for validation. Satisfactory results were achieved for the validation. The Q3 model was run in a child restraint system in a simulated 48 km/h frontal crash on a test bench. The response of the Q3 was compared to the simpler MADYMO Q3 model and the Hybrid III 3-year old dummy. Finally, the spine box was modified to improve the biofidelity of the dummy model.