BackgroundThe development of Web-based interventions for substance abuse in Latin America is a new field of interest with great potential for expansion to other Spanish-speaking countries.ObjectiveThis paper describes a project aimed to develop and evaluate the usability of the Web-based Help Program for Drug Abuse and Depression (Programa de Ayuda para Abuso de Drogas y Depresión, PAADD, in Spanish) and also to construct a systematic frame of reference for the development of future Web-based programs.MethodsThe PAADD aims to reduce substance use and depressive symptoms with cognitive behavioral techniques translated into Web applications, aided by the participation of a counselor to provide support and guidance. This Web-based intervention includes 4 steps: (1) My Starting Point, (2) Where Do I Want to Be? (3) Strategies for Change, and (4) Maintaining Change. The development of the program was an interactive multistage process. The first stage defined the core structure and contents, which were validated in stage 2 by a group of 8 experts in addiction treatment. Programming of the applications took place in stage 3, taking into account 3 types of end users: administrators, counselors, and substance users. Stage 4 consisted of functionality testing. In stage 5, a total of 9 health professionals and 20 drug users currently in treatment voluntarily interacted with the program in a usability test, providing feedback about adjustments needed to improve users’ experience.ResultsThe main finding of stage 2 was the consensus of the health professionals about the cognitive behavioral strategies and techniques included in PAADD being appropriate for changing substance use behaviors. In stage 5, the health professionals found the functionalities easy to learn; their suggestions were related to the page layout, inclusion of confirmation messages at the end of activities, avoiding “read more” links, and providing feedback about every activity. On the other hand, the users said the information presented within the modules was easy to follow and suggested more dynamic features with concrete instructions and feedback.ConclusionsThe resulting Web-based program may have advantages over traditional face-to-face therapies owing to its low cost, wide accessibility, anonymity, and independence of time and distance factors. The detailed description of the process of designing a Web-based program is an important contribution to others interested in this field. The potential benefits must be verified in specific studies.Trial RegistrationInternational Standard Randomized Controlled Trial Number (ISRCTN): 25429892; http://www.controlled-trials.com/ISRCTN25429892 (Archived by WebCite at http://www.webcitation.org/6ko1Fsvym)