Recent report on fish hook effect by Zhu and Liow [Chemical Engineering Science 111(2014) 94-105] involves size analyses using laser diffractometry. Since their test materials contain a significant amount of submicron particles, the refractive index and extinction coefficient of the particles have a major impact on the size analyses results. As such, if correct optical parameters are not used systematic errors in size analyses are inevitable. The data of Zhu and Liow are subject to this uncertainty. As a result, while their size analyses are repeatable, the accuracy is indeterminate. The reproducibility of their data is also questionable. Consequently, their results and conclusions on fish hook are to be treated with caution. (C) 2014 Elsevier Ltd. All rights reserved.