Product-by-Process (PBP) claims define a product by its method of manufacture, distinguishing them from standard claim formats. In 2011Hu927, the Korean Supreme Court adopted the product-per-se approach regardless of whether the claim was “true”or “pseudo.”In 2013Hu1726, the Court reaffirmed this as the principle for determining claim scope, while allowing an exception in cases of “manifestly unreasonable circumstances.”However, the exact meaning of such circumstances remains debated. This article reviews Korean jurisprudence and compares it with Japan, the EPO, and the United States. It proposes that clarity should be assessed by whether a person skilled in the art, considering the specification, drawings, and common knowledge at the filing date, can clearly identify the product defined by the process. For claim scope, the product-per-se rule should remain the principle, but when a limitation is necessary, the restriction should apply to the structure or properties defined by the process, not the process itself. This approach aims to ensure both doctrinal consistency and practical operability of the product-per-se principle maintained by the Korean Supreme Court.