Sooner or later, on-line methodologies are bound to become an important part of psychotherapy and/or psychological intervention. Among the first questions that arise are those related to professional ethics, since these new learning environments introduce new contexts and situations that are not provided for in current deontological guidelines. To address this question, a number of work groups active in the field of health sciences have devised ethical codes. However, none of these codes make specific reference to ethical principles in on-line psychotherapy. As a result, the Ethical Commission of the College of Psychologists of Catalonia has created a work group for application iiz clinica psychology and psychotherapy a set of basic ethical principles. We review the ethical principles presented in the best known codes and put forward our proposal for guidelines for psychotherapy and psychological intervention.