Background <p>Semantic transparency is typically defined in terms of compositionality, the extent to which the meaning of a word can be predicted from the meaning of each of its constituents, which is crucial for the processing of compound words. Studies employing behavioral, eye-tracking, and neuroimaging techniques have identified common effects of semantic transparency. Transparent words, defined as those in which the word itself and its morphemes exhibit a high degree of semantic relatedness, facilitate word recognition. Semantic transparency effects have been well observed for alphabetic languages. However, the effects of semantic transparency on Chinese readers are largely unknown, as do whether healthy aging may affect this effect. The present study investigated these questions by analyzing the semantic transparency effects in both young and older adults under conditions of normal reading and preview.</p> Methods <p>The eye movements of young (18–25 years) and older (60 + years) Chinese readers were recorded under conditions of normal reading and preview.</p> Results <p>(1) Transparent words facilitated word recognition and the valid preview clues did not benefit readers recognizing transparent words. (2) Age groups showed no differences in the process of compound words. However, older adults had greater difficulty recognizing opaque words under preview conditions than younger adults.</p> Conclusions <p>Compound words are stored in the mental lexicon as mixed representations, in which transparent words are represented by morphemes and opaque words are represented by whole words. Semantic transparency effects exhibit cross-age consistency which do not rely on valid preview information but instead stem from foveal in-depth processing. However, age differences in semantic integration become apparent in parafoveal preview processing which demands greater cognitive resources, with older adults experiencing greater difficulty recognizing opaque words than younger adults.</p>