Therapy can come in a variety of formats, including individual psychotherapy, group psychotherapy and electronic/internet e-therapy.
In the individual format, a single psychotherapist meets with a single client or patient one or more times per week for about 50 minutes each meeting. Patients have the therapist's full attention during an individual session, which may help the session to feel more secure and safe. The individual format encourages patients to explore their difficulties in-depth across multiple sessions in a way that is not possible in group format psychotherapy.
Group psychotherapy pairs one or more therapists with five to ten patients for 90 minutes or so. Group psychotherapy sessions with a 'teaching of coping skills' agenda are run like classrooms, with the therapist acting as teacher, and the patients acting like students. Usually the therapist will teach some important concept, and then will encourage the patients to give examples of that concept from their own lives. Group therapy is also often run in a 'support' or 'growth' mode, wherein the therapist will guide the patients in a discussion of things they are struggling with in their lives. Without overpowering the discussion itself, the therapist attempts to shape it so that the participants support one another, model effective ways of managing problems, and get relatively equal chances to talk.
Group therapy formats are cheaper to participate in, and often are just as effective or more effective as individual forms of therapy. Group psychotherapy participants are able to learn from one another in addition to the therapist. Drug and alcohol dependent people often have problems with authority, and may be more able to hear and learn things from their peers than they are from therapist/authority figures.
Internet psychotherapy (eTherapy) is an intervention in its infancy. Not much is known about how effective it is in any systematic, scientific way. However, it does offer certain characteristics that are unique and that may appeal to some patients. E-therapy is cheaper than conventional (individual) psychotherapy, and as private as individual therapy. It also has some downsides: E-therapy occurs via email in text format, meaning that in order to participate in this sort of therapy, patients have to be good at expressing themselves verbally. There is also no eye-contact possible in this sort of therapy, making it easier for patients to hide things from the therapist (although this may occur in any form of therapy). Given these considerations, E-therapy is probably not an optimal form of therapy for addicts at this time.
It is often desirable to mix and match different types of psychotherapy to provide a more custom fit to a given patient's needs. Supportive psychotherapy (offered in a group format) might be combined with coping-focused relapse prevention (also offered in a group setting). Individual supportive therapy might be combined with participation in a group format social skills/interpersonal/growth therapy setting. Such combining of types and modes of psychotherapy can be very useful, but is often limited by a patient's access to resources.