Since there is a widespread belief that sports contributes to a healthy development, coaches, parents and other representatives acting in the sport environment are often expressing a concern about the high drop-out rate in organized youth sports. However, drop-out decisions made by youths are not a static phenomenon (Patriksson, 1988). In order to be able to capture the mobility, the aim of the study was to examine longitudinal (2 years, 3 waves) changes of participation and drop-out patterns based on self-reports of 920 youth (10-18 years) from Sweden. Results showed that a vast majority (93%) of participants had, to some extent been involved in organized sports when entering the last wave. The participation rate decreased with 7% (75-68%) between 10-12 years, with 13% (66-53%) between 13-15 years and with 8% (42-34%) between 16-18 years. The attrition rate was highest between the ages of 14-16 (19%). Every year, a significant proportion (19%) of those who dropped out of sports returned. Almost a fifth of those who have dropped out of sports returned, but once again withdraw in the same year. A higher proportion of girls than boys (46% vs 37%) withdraw from sports. Further analyses revealed that it is primarily girls with foreign background who drops out. Results also showed that those who drop-out of sports to a larger extent are physical more active (twice a week or more) when compared with those who never have been involved in organized sports (64-66% vs 45-50%). The results are discussed in relation to longitudinal trends shown in previous research (e.g., Findlay, Garner & Kohen, 2009; Patriksson, 1988; Seippel, 2005) but also in relation to studies that have only used cross-sectional or retrospective designs (e.g., Butcher, Lindner & Johns, 2002).