The Conceptual Survey of Electricity and Magnetism (CSEM) covers a large conceptual domain and gives many opportunities for comparing the difficulties of different conceptual areas in electricity and magnetism. Six conceptual areas were identified in the CSEM that are represented by groups of four to six questions each. The CSEM was administered as a posttest to 84 Croatian students in a calculus-based general physics course at the University of Zagreb. The average difficulties in the six conceptual areas were compared to the average difficulties of the same conceptual areas of American students enrolled in algebra-based or calculus-based general physics courses. The difficulties of the conceptual areas show similar trends for the three groups of students. The most difficult area was found to be electromagnetic induction, followed by Newton's laws in the context of electricity and magnetism, together with the electric potential and energy. The comparison of pretest and posttest results suggests that instruction in both algebra-based and calculus-based courses is not efficient in reducing the pretest difficulties of the conceptual areas; however, the impact of instruction differs among conceptual areas.