Representational competence is defined as "skills in interpreting and using representations". This study attempted to compare students' of high, medium, and low levels of understanding of (1) basic chemical concepts, and (2) chemical representations, in their representational competence. A total of 411 Form 4 science students (mean age = 16 years) from seven urban secondary schools in Malaysia participated in this study. Data were collected from three instruments namely the test of chemical concepts, the test of chemical representations, and the test of representational competence. The Statistical Package for the Social Sciences was used to analyze the data. Findings showed students with a high level of understanding of (1) chemical concepts and (2) chemical representations had significantly higher overall level of representational competence compared to both the medium and the low groups, at p < 0.001. However, students with medium and low levels of understanding of (1) chemical concepts and (2) chemical representations showed no significant difference in their overall levels of representational competence. Findings also showed that students' overall level of representational competence had a higher dependence on their level of understanding of chemical concepts than their level of understanding of chemical representations.