In this paper, the actual diet of children and adolescents is characterized by food group intake. Age-dependent dietary patterns and long-term dietary trends are described and commented on against the background of the optimized mixed diet, a preventive total diet concept for German children and adolescents. Dietary intake data come from 3-day dietary records obtained in the DONALD Study (Dortmund Nutritional and Anthropometrical Longitudinally Designed Study), an ongoing mixed longitudinal cohort study conducted at the Research Institute of Child Nutrition since 1985. The actual diet of the observed children and adolescents differed to some extent from the optimized mixed diet. For example, the intake of vegetables was lower and the intake of meat/sausage and confectionary was higher than recommended. The three rules for food selection of the optimized mixed diet (consume plant foods and beverages liberally, animal foods moderately, and high-fat, high-sugar foods occasionally) show a practical way to improve unfavorable dietary habits of children and adolescents without fundamental changes of food intake patterns and taste properties of the actual diet. The partly favorable and partly unfavorable dietary trends observed in the DONALD Study should continue to be critically considered.