This study examines the relationship between advertising agency and clients, centering around the agency-client life cycle(pre-relationship stage, development stage, maintenance stage, and termination stage). Findings through in-depth interviews suggest that differences exist between advertising agency and clients in terms of four stages of the agency-client life cycle. When it comes to selecting an advertising agency, clients chose agency’s digital marketing competency and expertise while advertising agencies chose creativity. In terms of the rejection fee, both advertising agencies and clients agreed upon payment rejection fee. Advertising agencies are strongly in favor of payment rejection fee because rejection fee could be considered to be a reward for their expertise and effort. However, clients also expressed their concerns that it is difficult to calculate rejection fee. Factors which positively affect the relationship between advertising agencies and clients are agencies’ expertise and respect for agencies’ expertise. From clients’ perspective the positive relationship forms when agencies lead project with their expertise. And from agencies’ perspective the positive relationship forms when clients respect agencies’ expertise. In terms of factors negatively affecting the relationship between agencies and clients, agencies, agencies considered clients’ bossiness (i.e., Gapjil) as the most important whereas clients considered agencies’ low credibility, difficulty of communication, and low commitment on projects as important factors.