Trials to confirm the scope of patents are the trials that a patentee, an exclusive licensee or an interested person demands to confirm whether the scope of a patent right includes an invention that is being carried out or is going to be carried out. Passive trials to confirm the scope of patents are to confirm that an invention does not fall in the scope of a patent. This article investigates the development of passive trials between patents and highlights the problems included in the cases in dealing with those trials. In addition this article tries to suggest solutions to the problems and propose amendment of Korean Patent Act. Decisions by the Korean Supreme Court on passive trials to confirm the scope of patents can be summarized as follows: ① Trial to confirm the scope of a patent against another patent is illegitimate in principle. ② Passive trial to confirm the scope of patents is legitimate because even though such trial is admitted, it does not result in invalidation of another patent. ③ Passive trial to confirm the scope of patents is legitimate because the claimant has risked the possibility of his patent to be invalidated. ④ The court can make a decision that denies the validity of the clamant's patent in a passive trial to confirm the scope of patents These judgements of the Supreme Court show that there are too many legitimate cases among trials to confirm the scope of a patent against another patent to rule that such trials are illegitimate 'basically'. According to the Supreme Court, all trials to confirm that a patent does not fall in the scope of another patent are legitimate. Examination of the development of the cases of the Supreme Court reveals that these recent cases do not harmonize with the early cases. Because atest decisions of the Supreme Court have become to be different from those of earlier ones, it is needed to clarify the definition of 'trials to confirm the scope of patents' and the legitimacy of passive trials between patents.