The main aim of this thesis was to increase understanding of the decision processes and strategies underlying line-up identifications in child and adult eyewitness. In the first experiment, 8- to 10-year-olds witnessed a staged-crime event then identified the target from a sequential, fast elimination or slow elimination line-ups. Measures of children's pre-decision and post-decision confidence were also obtained. Correct identifications of the target were significantly higher with the fast elimination line-up. A main effect of line-up type was not found in target-absent conditions. Possible explanations for these findings are discussed and some limitations of the experiment are highlighted. Experiment 2 examined the identification accuracy of 5- to 6-year-olds, 9- to 10-year-olds and adults in target-present and target-absent simultaneous, sequential and fast elimination line-ups. Measures of children's and adults pre-decision and post-decision confidence were also obtained. Age related differences in identification accuracy were found such that 5- to 6-year-olds were less likely than 9- to 10-year-olds or adults to make a correct line-up rejection. However, 9- to 10-year-olds' correct rejections were equivalent to adults'. Both groups of children were less likely than adults to correctly identify the target with a sequential line-up. Experiment 3 aimed to establish whether seeing the line-up members as moving images would influence children's discrimination of line-up members. Identification accuracy of 5- to 6-year-olds, 9- to 10-year-olds and adults was examined across Target-absent conditions of simultaneous line-up and fast elimination line-ups. The results from this experiment were found to be comparable to those of Experiment 2 such that 9- to 10-year-olds' correct rejections were equivalent to adults.