The needs of drug users for substitution therapy and drug-use-related care can vary greatly, a source of conflict between users and health care professionals and sometimes generating dysfunction of the health care system. For example, in France the lack of injection formulations for substitution therapy has led users to inject their substitution product (Subutex or Skenan) creating a bogus relationship with the pharmacist or physician who do not know how they should react. Beliefs held by health care professionals and the lack of drug abuse training in the pharmacy and medicine curricula can also lead to a dangerous situation for users: physicians may prescribe a dose too low for substitution with the risk of pushing the user into the black market to search for a complement. We detail here the way users would like to use substitution, focusing on the points where they are in agreement or disagreement with health care professionals. We explain why, in our opinion, it is fundamental to take into consideration the users' point of view.