The aim of this thesis was to investigate the use of mobile phones as an adjunct to face-to-face psychotherapy. This aim was developed from two structured reviews of the literature concerning the types of adjunctive technologies in use, and the ways in which they have been used to increase adherence. Adjunctive use of the mobile phone was investigated in regards to its capacity to achieve greater client adherence and engagement in therapy, in order to facilitate improved treatment outcomes and client satisfaction. This overarching aim and hypothesis was investigated in three empirical studies, presented as a series of published and unpublished papers. Study One investigated the use of Short Message Service (SMS) appointment reminders. It was predicted that the SMS prompts, delivered the day prior to a scheduled appointment at an outpatient psychology clinic, would decrease client non­ attendance and dropout. In a Randomised Controlled Trial (RCT), 140 participants were allocated to either receive SMS appointment reminders or to receive no reminders. No significant differences were found between the two conditions in relation to client attendance. Dropout was higher in the SMS condition than in the no SMS condition. It was concluded that the SMS reminders did not increase client adherence to appointment attendance behaviours. This study also highlighted the importance of careful examination of technological interventions before dissemination.