Congenital disorders of glycosylation (CDG) are genetic multisystemic diseases due to various defects in the biosynthesis or processing of glycoproteins. Our aim is to present our experience in the selective screening of CDG syndrome in a paediatric population (421 patients) with clinical suspicion of the disease, analysing serum carbohydrate-deficient transferrin (CDT) by radioimmunoassay and/or immunoturbidimetry. We established the normal values for our paediatric population. The abnormal results were confirmed and classified by isoelectric focusing of serum sialotransferrins, and by enzymatic and molecular studies. We found 14 patients (3.3%) with abnormal serum CDT; 11 of them were classified as CDG type Ia (CDG-Ia) and the other three showed altered isoelectrofocusing patterns but remain untyped and are under investigation. In conclusion, both CDT assays proved to be useful tools for CDG screening. Isoelectric focusing is a simple procedure but it requires specific instruments that are not always available. Since the immunoturbidimetric procedure is commonly used to monitor for recent excessive alcohol consumption in clinical laboratories and does not require special equipment, it may also be reliably used to screen for CDG in children under clinical suspicion.