Background: Coffee silver skin is a by-product generated during the processing of coffee, which has recently been cultivated mainly in the southern regions of Korea. Radical scavenging active compounds were analyzed as part of a study of active compounds present in coffee silver skin. Methods and Results: Hot water extracts and ethanol extracts were prepared at varying concentra- tions (10% - 95%). Simultaneously with liquid chromatography (LC) separation, 1,1-diphenyl-2- picrylhydrazyl radical scavenging activity was measured and mass spectrometry (MS) of the iden- tified radical scavenging active compound peak was performed. The analysis results confirmed the presence of three compounds, eicosanoyl-5-hydroxytryptamide, docosanoyl-5-hydroxytryptamide, and tetracosanoyl-5-hydroxytryptamide. In the rapid LC-MS/MS analysis using the multiple reac- tion monitoring mode, each active compound showed a higher content as the ethanol concentration increased. In particular, the content of each compound was found to be significantly decreased in the extract with an ethanol concentration of 60% or less. Conclusions: The three identified alkanoyl-5-hydroxytryptamide compounds are reported to pos- sess antioxidant activity and various neurological disease-related effects. Therefore, this analysis method can be applied to research or product development using coffee silver skin