Nowadays, PD-L1/PD-1 immune checkpoint inhibitors have become a key part of the clinical management of cancer. Improving our understanding of anti-cancer immune response, which is influenced by a complex set of tumour, host and environment factors, will further broaden the clinical applicability of these treatments. In this review, we discuss several approaches to evaluate the tumour microenvironment (TME) in clinical practice as well as a view on future predictive biomarkers for cancer immunotherapy.