The aim of this study was to present a new working memory test following the line of work started by García-Madruga et al. (2007) and to examine its relation to reading comprehension and propositional reasoning measures. In that study we designed a new working memory span test –based on Daneman & Carpenter's (1980) Reading Span Test (RST)– in which the processing task called for an inferential decision –to resolve a pronominal anaphora based on Morpho-Syntactic cues– and had people recall the result of this inference. In the current study, besides the RST and the Morpho-Syntactic Anaphora test, we presented a new Semantic Anaphora measure. In order to check the validity of this new Working Memory (WM) task, we used the same reasoning task used in the previous study as well as a new reading comprehension test. The results show the tight relationship amongst working memory, reading comprehension and reasoning, and confirm the validity of the new WM measure.