Content unchanged new edition. Research on the development of children's Theory of Mind has primarily focused on understanding beliefs. The investigation of understanding desires has largely been overlooked. This work provides a comparative examination of the developmental trajectories of desire and belief understanding. In a longitudinal study, children aged 3.5 years were presented with tasks related to desire and belief over ten sessions spanning seven months. A second study explored how desire and belief understanding manifests in children aged 3 years. The results of both studies support a gradual development of representational understanding. Children between the ages of 3 and 3.5 years begin to slowly grasp the representational structure of desires.