This study investigated the effectiveness of combining conceptual change text and discussion web strategies on students' understanding of photosynthesis and respiration in plants. Students' conceptual understanding of photosynthesis and respiration in plants was measured using the two-tier diagnostic test developed by Haslam and Treagust (1987, "Journal of Biological Education" 21: 203-211). The test was administered as pretest and posttest to a total of 233 eighth-grade students in six intact classes of the same school located in an urban area. The test of logical thinking was used to determine the reasoning ability of students. The experimental group was a class of 116 students received discussion web and conceptual change text instruction. A class of 117 students comprised the control group received a traditional instruction. After instruction, data were analyzed with two-way analysis of covariance (ANCOVA) using the Test of Logical Thinking and pretest scores as covariate. The conceptual change instruction, which explicitly dealt with students' misconceptions, produced significantly greater achievement in understanding of photosynthesis and respiration in plant concepts. Analysis also revealed a significant difference between performance of females and that of males in the favor of females, but the interaction of treatment with gender difference was not significant for learning the concepts.