The purpose of this study was to validate instruments to measure the preferences and immediate demands that compete with the conduct of physical activity. A study was conducted of methodological validation of instruments applied to a group of 928 young people (542 women and 386 men) high school students and undergradute student, using the stratified random sampling1 in k (range 57-99). The instruments of preferences and immediate demands that compete with the conduct of physical activity showed a alpha of .865 and .862 respectively. The analysis of the construct validity of the instruments threw eight factors that together explain the 49.34 % of the variance for the instrument of preferences and six factors that explained the 58.24 % of the total variance for the instrument of demands. The study shows two instruments with good reliability and validity. The preferences of behaviors of rest, use of the technology, as well as the family demands, work and school are the factors that explained the greater percentage of total variance. These instruments will be useful to measure the preferences and immediate demands that compete with the physical activity of young people and may be used by professionals in the physical activity and sport, as well as those associated with the prevention of health.