In this study, we identified the code-related (decoding, fluency) and language comprehension (vocabulary, listening comprehension) demands of the CBM-Maze test, a formative assessment, and compared them to those of the Gates-MacGinitie test, a standardized summative assessment. The demands of these reading comprehension tests and their developmental patterns were examined with multigroup structural regression models in a sample of 274 children in Grades 4, 7, and 9. The results showed that the CBM-Maze test relied more on code-related than on language comprehension skills when compared to the Gates-MacGinitie test. These demands were relatively stable across grades.