Research reported by Sifonis (2008) has demonstrated that the type of comparison made during analogical problem solving affects the quality of the ideas generated. Ideas generated by mapping the differences between domains are rated as less practical than ideas generated by mapping similarities between domains. However, ideas generated by mapping the differences between domains are more creative than ideas generated by mapping the similarities. The current study examines whether these effects of comparison could be due to mapping alignable or nonalignable differences between domains. The data used in the Sifonis (2008) study were examined to determine whether participants used alignable or nonalignable differences between domains to generate ideas for the source domain. Analyses indicated that ideas generated using alignable differences are more practical than ideas generated using nonalignable differences. Ideas generated using nonalignable differences are more creative than ideas using alignable differences. Practical applications of these findings will be discussed.