This research was conducted to investigate 7th grade students' problem solving success rates on proportional reasoning problems and whether these success rates change with different problem types. 331 randomly selected students of grade seven participated in this study. A problem test which contains three different types of missing value (direct proportional, inverse proportional and additive/non-proportional) word problems was designed as a data collecting tool for the research. Descriptive data analysis methods were used in this study. Analysis has shown that 7th grade students solved different problem types with different success rates. The findings of the study also indicate that problem types affect students' problem solving performances.