Recent composition languages like BPEL allow for composing single Web Services as higher-level business workflows. Runtime engines obtain the task to deploy and to publish these processes as regular Web services that can be located and used by any client. These runtime engines, however, do not enable end-users to flexibly adapt the constructs that represent a workflow in a personalized manner. The claim of this work is that end-user adaptability (tailorability) of personalized workflows will be increasingly significant for future applications. Based on our experience with component-based tailoring methods, we propose the multi-tier architecture TailorBPEL that supports the tailoring of personalized BPEL-based workflow compositions.