Business processes are frequently subject to changes which must be supported by process models and systems implementing them. This paper deals with adaptability of Inter-Organizational Workflow (IOWF) process models based on services. It states conceptually, typical adaptations that can be operated on IOWF models obeying to the chained execution architecture. IOWF models are described through the concepts of service and orchestration function expressed using basic control flow operators. Thus, operations of adaptation turn to modification of services and transformation of orchestration functions describing the model. We particularly distinguish evolvable adaptation leading to expansion of the cooperation and/or the global functionality of the process.