This research explored the effects of three types of multimedia glosses on the reading comprehension of learners in an EFL context. From among the three experimental groups under study, one received treatment on five academic reading passages through picto-textual glosses where both textual definitions and relevant images of words popped up, thus helping learners surmise the meanings of the keywords. In a similar vein, the other two groups received treatment on the same passages, but used either pictorial or textual glosses where pertinent pictures or textual definitions of the keywords appeared on the screen. The experiment showed that the picto-textual-gloss group outperformed the other two groups, and that the pictorial-gloss group outperformed the textual-gloss group. The study thus underpinned Paivio's (1971, 1986, 1991) Dual Coding Theory, arguing that when information is available in two modes of presentation, it becomes more elaborate and thus more memorable. When applied to reading comprehension, the idea suggests that the combination of textual and visual definitions might help learners better decipher the meanings of keywords in reading passages, and hence arrive at an even deeper comprehension of the texts.