Process evaluations can help us to better interpret intervention effects and provide guidance in improving interventions. This study describes the use and appreciation of FATaintPHAT, a computer-tailored intervention to prevent excessive weight gain in adolescents and link these data to the intervention effects. Use and appreciation were assessed among students (12-13 years old) from the intervention group of the FATaintPHAT evaluation study, using computer log (n = 458) and questionnaire data (n = 233, 48% response). Differences in use and appreciation between socio-demographic groups (gender, education, ethnicity, weight category), and associations with behavioural outcomes were analysed using descriptive and regression analyses. The results showed that a majority of the students (81%) was exposed to all intervention modules and 73% reported to have put the advice into practise. Half and one-third of the students appreciated the tailored advice positively and neutrally, respectively. Students attending vocational training appreciated FATaintPHAT better than students attending university preparation education. No associations were found between behavioural outcomes with appreciation and use. In conclusion, the school-based FATainPHAT intervention was used and appreciated well among adolescents. The fact that the intervention was appreciated better among the lower compared with higher educated students indicates that the technique of computer-tailoring is also suitable for lower educated students.