Purpose: In text comprehension, sentence level syntactic processing is crucial for establishing who did what to whom. Furthermore, efficiency in applying this knowledge may help accurate text comprehension because efficiency releases resources for higher cognitive processes, such as inference generation. The main purpose of the present study was to investigate to what extent sentence processing efficiency explains variance in text comprehension beyond reading fluency and vocabulary. Such a result would confirm that for the practical purpose of text comprehension, there is a separation between individual differences in syntactic and vocabulary processing. Previous studies have shown that grammar knowledge is a predictor of reading comprehension (e.g. Adolf, Catts & Lee, 2010; Silva & Cain, 2014), but it is unclear which particular aspects of grammar knowledge are important. Thus a secondary purpose was to investigate whether processing of difficult syntactic constructions (e.g. passive and object relative clauses) is more indicative of reading comprehension difficulties than knowledge of easier parallel constructions (e.g. active and subject relative clauses). Method: Eighty Danish Grade 5 students completed tests of reading comprehension, word reading fluency, vocabulary, working memory, and sentence processing. In the sentence processing task, students read one sentence at time and answered comprehension questions about the interpretation of thematic roles. We measured comprehension accuracy and response times to compute efficiency scores. The sentence materials consisted of a balanced number of easy and difficult constructions. Results: Both sentence comprehension question efficiency explained unique variance in reading comprehension beyond control measures including vocabulary. Additionally, comprehension efficiency on difficult constructions explained variance in reading after controlling for comprehension efficiency on easy sentences. Conclusion: Text reading comprehension appears to rely on both accuracy and efficiency of sentence processing. The results suggest that individual differences that are in sentence processing that are relevant for text comprehension are at least partially independent of vocabulary knowledge. The results also suggested that students’ syntactic processing skills are related to text comprehension.