ISO 9001 deals mainly with customer complaints about quality, whereas ISO/IEC 20000-1 and ISO/TEC27001 are IT focused

ISO/IEC 20000-1 applies to service management, whereas ISO 9001 and ISO/IEC 27001 can NOT be used effectively in a service provider organization

An SMS can be integrated with a quality management system based on ISO 9001 or an information security management system based on ISO/IEC 27001

It is necessary for service provider organizations to be certified against all of them to ensure an effective service management system