The objectives of the research is to study theattitude of Advertising Agency and the client'scommunication behavior in order to gain the corporationbetween two parties. Communication problems arisingbetween clients and Advertising Agency is alsoexamined. 16 Advertising Agency and 20 clients are alsoselected as the key informants. Theory of CommunicationProcess and Interpersonal Communication is theconceptual framework for analysis. The results are 1) Most of the attitude ofAdvertising Agency are the satisfaction with client'scommunication behavior because they are consequentlywell corporative. However, for some who areunsatisfactory due to the ineffectiveness incommunication behavior which make the cooperation moredifficult. Regarding to advertising Agency suggestion,it is their responsibility to adapt themself andflexible to the clients' needs. 2) It is clear that theproblem of client's communication behavior involve withunclear data, unproperly information, or informationselection, ambiquity, misintepretation, firstimpression, halo effect and identity cues. 3) It isfound that main courses of problem come from the lackof experiences and knowledge in Advertising field onthe side of the clients. Moreover, there still havepersonal problems, too-strict policy, poor preperationin communication and also trustworthy and creditabilityof being teamwork.