In a method and device for preparation of a medicament for the treatment of lungs having a surfactant deficiency, a sample from a patient is quantitatively analyzed with regard to at least one of the proteins SP-A, SP-B, SP-C and SP-D, a determination is made as to whether a deficiency of one of the analyzed protein SP-A, SP-B, SP-C or SP-D exists and if that is the case, a determination is made of a therapeutically effective dose of a replacement substance for the analyzed protein SP-A, SP-B, SP-C or SP-D, and a medicament containing the therapeutically effective dose of the replacement substance is prepared.