Purpose: This study was conducted to identify late school-aged children‘s knowledge, and practical will in the practice of cancer prevention lifestyle, and to examine the relations between these variables and factors that influence practice. Methods: The participants included 525 fifth and sixth grade students from 8 elementary schools in J and S cities. Data were collected in December 2008 using self-report questionnaires developed by the authors and were analyzed using the SPSS program. Results: Mean scores were, for knowledge of cancer prevention lifestyle, $0.76{pm}0.11$ out of a possible 1, practical will, $4.05{pm}0.55$ out of a possible 5, and practice, $3.66{pm}0.41$ also out of 5. There were differences in knowledge (F=4.39, p=.013), practical will (F=18.35, p<.001), and practice (F=29.13, p<.001) according to academic achievement and in practical will (F=3.68, p<.001) and practice (F=3.01, p=.003) according to grade. There were positive correlations between knowledge and practical will (r=.205, p<.001), knowledge and practice (r=.181, p<.001), practical will and practice (r=.628, p<.001). Practice will and knowledge of cancer prevention lifestyle showed a significant influence on practice. Conclusion: Results of this study indicate that effective strategies should be developed to motivate the practical will for the practice of cancer prevention lifestyle during childhood.