This study applied confirmatory factor analyses to explore the factor structure of the Fortitude Questionnaire (FORQ) in three samples: adolescents, students and lay counsellors. For the student and lay counsellor samples, the analysis demonstrated that a bifactor and a three-factor second-order model of the FORQ was a much better fit than a one-factor model, whilst in the adolescent sample, there was no discernible difference between the three models. Ancillary bifactor analysis was also conducted to examine the dimensionality of the FORQ. The bifactor measures confirmed that the FORQ is not unidimensional, but rather multidimensional for the student and lay counsellor samples. For the adolescent sample, there are some concerns as the general factor accounted for 77% of the variance, whilst the subscales accounted for only 23% of the variance. Furthermore, in the standardised solution for the adolescent sample, only the factor loadings for the total scale were significant. In addition, the model-based estimates of reliability were low for the self-appraisal and support-appraisal subscales in the adolescent sample. This finding indicates that the FORQ was essentially unidimensional in the adolescent sample. These results suggest that for young adult and adult samples, the FORQ may be utilised as a total scale and three subscales, whilst in adolescent samples, caution needs to be applied in using the FORQ subscales with children and adolescent samples. However, further research that replicates this finding in adolescents and other samples is needed before a definite conclusion about the suitability of the FORQ in different age groups can be reached.