Background Decision-making in initiating life-sustaining health technology is complex and often conducted at time-critical junctures in clinical care. Many of these decisions have profound, often irreversible, consequences for the child and family, as well as potential benefits for functioning, health and quality of life. Yet little is known about what influences these decisions. A systematic review of reasoning identified the range of reasons clinicians give in the literature when initiating technology dependence in a child, and as a result helps determine the range of influences on these decisions. Methods Medline, EMBASE, CINAHL, PsychINFO, Web of Science, ASSIA and Global Health Library databases were searched to identify all reasons given for the initiation of technology dependence in a child. Each reason was coded as a broad and narrow reason type, and whether it supported or rejected technology dependence. Results 53 relevant papers were retained from 1604 publications, containing 116 broad reason types and 383 narrow reason types. These were grouped into broad thematic categories: clinical factors, quality of life factors, moral imperatives and duty and personal values; and whether they supported, rejected or described the initiation of technology dependence. The majority were conceptual or discussion papers, less than a third were empirical studies. Most discussed neonates and focused on end-of-life care. Conclusions There is a lack of empirical studies on this topic, scant knowledge about the experience of older children and their families in particular; and little written on choices made outside 'end-of-life' care. This review provides a sound basis for empirical research into the important influences on a child's potential technology dependence.