Previous studies on dictionary consultation investigated mainly online dictionaries or simple pocket electronic dictionaries as they were commonly used among learners back then, yet the more updated mobile dictionaries were superficially investigated though they have already replaced the pocket electronic dictionaries. These studies are also limited in that they concentrated generally on intentional learning and have not much inspected the significance of dictionary consultation for incidental learning. Moreover, most of them selected monosemous words as target lexical items, yet the learning of polysemous words has not been examined in depth. Therefore, in response to the call for research on the effectiveness of mobile dictionary consultation in promoting incidental learning of polysemy, we conducted an experiment among 82 intermediate Cantonese English as a Foreign Language (EFL) learners in Hong Kong, attempting to figure out what challenges these learners encountered while learning target words in the context of reading through consulting mobile dictionaries. These subjects were asked to comprehend a reading text with ten underlined target words, 32 of whom inferred meanings of these words and 50 looked them up using mobile dictionaries. The results of the study showed that mobile dictionaries facilitate word learning significantly, yet the format of these dictionaries is significant, and dictionary training is indispensable. [For full proceedings, see ED564162.]