Conversational passage retrieval relies on question rewriting to modify the\noriginal question so that it no longer depends on the conversation history.\nSeveral methods for question rewriting have recently been proposed, but they\nwere compared under different retrieval pipelines. We bridge this gap by\nthoroughly evaluating those question rewriting methods on the TREC CAsT 2019\nand 2020 datasets under the same retrieval pipeline. We analyze the effect of\ndifferent types of question rewriting methods on retrieval performance and show\nthat by combining question rewriting methods of different types we can achieve\nstate-of-the-art performance on both datasets.\n