This book contains revised selected papers from the 18th International Conference on Membrane Computing, CMC 2017, held in Bradford, UK, in July 2017. The 18 full papers presented in this volume were carefully reviewed and selected from 29 submissions. They deal with membrane computing (P systems theory), an area of computer science aiming to abstract computing ideas and models from the structure and the functioning of living cells, as well as from the way the cells are organized in tissues or higher order structures. The volume also contains 2 invited talks.