This review summarizes our current understanding of the metabolic syndrome (MetS) in children and adolescents. Special emphasis is given towards diagnostic criteria and therapeutic options. Consistent diagnostic criteria to define MetS in childhood and adolescence are not available to date. There is common agreement that the main features defining MetS include (1) disturbed glucose metabolism, (2) arterial hypertension, (3) dyslipidemia, and (4) abdominal obesity. However, settings of cut-off values are still heterogeneous in the pediatric population. Additional features that may define cardiometabolic risk, such as non-alcoholic fatty liver disease (NAFDL) or hyperuricemia, are not considered to date. Prevalence of childhood obesity has more than doubled since 1980, and 6-39% of obese children and adolescents already present with MetS, depending on the definition applied. There is common agreement that a consistent definition of MetS is urgently needed for children to identify those at risk as early as possible. Such definition criteria should consider age, gender, pubertal stage, or ethnicity. Additional features such as NAFDL or hyperuricemia should also be included in MetS criteria. Lifestyle modification is still the main basis to prevent or treat childhood obesity and MetS, as other therapeutic options (pharmacotherapy, bariatric surgery) are not available or not recommended for the majority of affected youngster.