In the setting of small cell lung cancer (SCLC), the development of immuno-oncological agents, particularly those targeting Programmed cell Death protein 1 (PD-1) and Programmed cell Death protein Ligand 1 (PD-L1), is still at an early stage. Two critical elements need to be considered : the current data are extracted from Phase I and Phase II trials and the level of evidence from phase III trials has not been reached as it has been for non-small cell lung cancer (NSCLC) or for malignant melanoma ; The second aspect is the slow development of predictive factors for response to the immuno-oncological agents targeting the PD-1 receptor and its ligand. The clinical data are still too fragmentary to produce recommendations, although the improvement in progression-free survival seen in different phase II studies is promising. The expectation of clinicians dealing withSCLC is an indication of the challenge that this disease currently poses to oncology and justifies a focused clinical research effort.