Increasing numbers of educational institutions are adopting an online approach to teaching and learning; however, little regard has been given to the prerequisite personal and technical qualities required for academic achievement and satisfaction within this environment. In recognition of this, researchers have been exploring the design, development and testing of diagnostic tools to assess student readiness for online learning. This study builds on previous work by the authors to further validate their diagnostic tool for assessing "Tertiary students' readiness for online learning" (TSROL) which has four subscales: "Technical skills", "Computer self-efficacy", "Learner preferences" and "Attitudes towards computers". Factor and reliability analyses revealed that Technical skills and Computer self-efficacy possessed good reliability and validity, and "Attitudes towards computers" fair reliability and validity. However, "Learner preferences" required revision as it possessed poor reliability and validity. Analysing the demographic data revealed that older students had lower Technical Skills and computer self-efficacy than younger students. The TSROL can be improved by adopting a more multidimensional interpretation of the Learning preferences and Attitudes towards computers subscales. (Contains 4 tables.)