In order to comfort others, children need to exhibit Theory of Mind (ToM) skills. The goal of the present study was to investigate the role of ToM in association with children's spontaneous comforting behaviour in a laboratory task. Forty-seven children between 26 and 57 months of age completed three ToM tasks: diverse desires, diverse beliefs and belief-emotion. To evaluate comforting, we used a previously evaluated procedure in which an experimenter drops a tower of blocks and pretends to be upset. The results showed a significant positive relationship between children's understanding of their own and others' desires and comforting. However, no relationships were found between comforting and understanding of one's own and others' beliefs or belief-emotion. The relationship between the different ToM tasks and age was also assessed, but it was non-significant. The implications of these findings for understanding the onset of spontaneous prosocial behaviour are discussed. [Translation from English by Mercè Rius.]