Abstract: The application of immunotherapy (IMT), especially immune checkpoint inhibitors, has brought revolutionary breakthroughs to cancer treatment, but only a few patients (10% to 30%) have shown a long-term response to the single therapy of IMT. In combination therapy, different drugs play a complementary or synergistic role, showing great potential. However, the therapeutic response rate of combined drugs varies greatly, and it may be accompanied by serious side effects while improving the therapeutic effect. Therefore, in order to use these treatments with good application prospects safely, effectively and widely, more research is needed. It is remarkable that immunoPET imaging is a useful tool for the development and the clinical transformation of combination therapy. The authors introduce several specific biomarkers that can be used to target immune activation, outline the recent progress of immunoPET imaging in exploration of cancer combination therapy, and discuss the development of such imaging methods in both preclinical research and clinical practice in the future.