This study focuses on examining senior high-school students' conceptual understanding and difficulties concerning electrochemistry and comparing patterns of thinking across Turkish and Indonesian contexts. The Electrochemistry Concept Questionnaire (ECQ) was applied to 516 Indonesian and 516 Turkish high school students right after the teaching of the electrochemistry topics. The ECQ contains 18 multiple-choice questions and these questions belong to five different categories: reactions occurring during electrolysis, differences between electrolytic and voltaic cells, movement of ions in voltaic cells, poles in voltaic cells, and voltaic cell reactions. At the end of the study, it was determined that both Indonesian and Turkish senior high-school students' understanding of electrochemistry concepts was relatively weak and they shared common difficulties concerning electrochemical concepts. While there was no significant difference between the average scores of the students from both countries on the test, it was determined that there were some significant differences on the basis of questions. It has been concluded that students from both countries have alternative conceptions similar to those determined in previous studies such as ''during electrolysis, the electric current produces ions'' and ''electrons migrate through the solution from one electrode to the other''. At the end of the study, the reasons for the similar results and the significantly different results for the students of the two countries to comprehend electro-concepts were discussed.