Using growth curve modeling, trajectories of undercontrolled (oppositional, irritable, inattentive and overactive behaviors) and internalizing (worried, sad and fearful) problems from 18 months to 4.5 years were studied in a population based sample of 921 Norwegian children. At the population level, undercontrolled problems decreased and internalizing problems increased with increasing age. Child temperament and family factors present at 18 months predicted 43% of the stability and 20% of the linear changes in undercontrolled problems and 30% of the stability and 7% of the linear changes in internalizing problems. Persisting effects of child and family factors from 18 month were found on the two problem dimensions over and above the impact of changes in the same risk factors. Lower initial level of partner support and higher initial level of child emotionality predicted higher slope of undercontrolled problems and higher initial level of family stress predicted higher slope for internalizing problems. As expected, time to time change (t1 to t2 and t2 to t3) in risk factors predicted time to time change in problem scores as well. The study shows the significance of early emerging internalizing and undercontrolled problems, the need to consider their pathways separately from very young ages, lasting effects of early experiences, and the importance of a dynamic approach to the analysis of risk.