Targeted therapy for cancer is a rapidly expanding and successful approach to the management of many intractable cancers. However, many immunotherapies fail in the longer term and there continues to be a need for improved targeted cancer cell toxicity, which can be achieved by radiolabelling the targeting vector with a radioisotope. Such constructs are successful in using a gamma ray emitter for imaging. However, traditionally, a beta emitter is used for therapeutic applications. The new approach is to use the short range and highly cytotoxic alpha radiation from alpha emitters to achieve improved efficacy and therapeutic gain. This paper sets out to review all experimental and theoretical comparisons of efficacy and therapeutic gain for alpha and beta emitters labelling the same targeting vector. The overall conclusion is that targeted alpha therapy is superior to targeted beta therapy, such that the use of alpha therapy in clinical settings should be expanded.