We present the results of a study of Chilean students' understanding of scientific models, using a Spanish-adapted version of the Students' Understanding of Models in Science instrument (Treagust, D. F., Chittleborough, G., & Mamiala, T. L. (2002). Students understanding of the role of scientific models in learning science. International Journal of Science Education, 24(4), 357-368. doi:10.1080/09500690110066485). The study covered 290 students in three schools in different parts of Chile. Results showed a Cronbach's alpha of 0.86 and medium correlation between the dimensions of the instrument. A confirmatory factor analysis showed that the five dimensions' theoretical structure is supported by the data, and one-way ANOVA and a t-test showed a balanced, non-discriminatory instrument that is suited for use in the Spanish language. The instrument also showed that Chilean students most need improvement in two of the dimensions - 'understanding of scientific models in terms of exact replicas' and the 'use of scientific models'. This reflects the original data analysed by Treagust et al. (2002) and suggests that these factors are common issues in the teaching and learning of scientific models. Future research will review the data by year and group to determine how students develop the idea of a scientific model and relate this information to science curricula. It will also investigate the link between students' understanding of scientific models and Anderson & Krathwohl's (2001) cognitive taxonomy.