The purpose of this study is to learn the meaning of being-a-child with cancer submitted to ambulatory treatment and using the toy library as a possibility to enable their expression about their world. Participants were seven children of ages 3 to 9 years, who had been diagnosed with some kind of childhood cancer. With the objective of learning about the meaning of these experiences to children with cancer, an analysis of these data was performed based on Martin Heidegger's existential phenomenology. The child-with-cancer showed a movement that was permeated sometimes by authenticity, when the child assumed the disease and their being-toward-death and also by the lack of authenticity, when they were influenced by the decadence attitude of their relatives and health team members. Playing provided a rich contact with the existence of these severely ill children.