Two adolescents (12 years old, suffering from acute lymphoid leukaemia (LLA) and 16 years old with acute myeloid leukaemia (LMA)) were treated with porcine surfactant (Curosurf). The indication for this treatment was a severe Respiratory Distress Syndrome (RDS) which appeared during leukaemia treatment. Pulmonary thrombo-embolism was suspected. The surfactant administered improved ventilation and oxygenation, enabling confirmation of the diagnosis which would otherwise have been impossible due to the seriousness of their condition.