Background: Children with developmental delay (DD) have a variety of problems indevelopmental functions. The purposes of this study were to analyze theunderlying diseases and risk factors in children with different functionaldelays.Methods: We collected data on 1048 children who underwent assessments of developmentalfunction, related diseases, and risk factors. All children were classifiedinto 6 functional delay groups: cognitive, speech, motor, pervasive,global, and non-specific DDs. Differences in related diseases and risk factorsof the 6 functional delay groups were determined.Results: Most children had global (51.2%), speech (21.9%), and motor (13.9%)delays. Approximately 62.8% of children were associated with biologicalfactors (19% with genetic defects or congenital anomalies, 16.5% with centralnervous system lesions, 13.9% with prematurity/low birth body weight,and 13.4% with neonatal insult). We could not identify the risk factors in36.6% of the children. Most children with motor delay had brain/neuromusculardiseases and were associated with risks of prematurity or low birthbody weight; while most children with global delay had brain neuromusculardiseases or psychological/mental disorders and were associated with risks ofgenetic defects or congenital anomalies.Conclusion: Our findings suggest that there are heterogeneous risk factors and related diseasesin children with different kinds of functional delay.