NEW CONTRIBUTIONS OF THE THESIS Thesis topic: Effect of diversification on business performance of enterprises in Vietnam Major: Commercial Business (Economics and Trade Management) Candidate: Pham Thi Thanh Huong Supervisors: Assoc Prof Dr Tran Van Bao Code: 62340121 Code: NCS33.042TM Dr Nguyen Minh Ngoc Training institution: National Economics University New contributions in academic and theory Firstly, By combining two methods of measurement of diversification - Entropy and Classification, the thesis provides a more detailed analysis of the effect of diversification on business performance The results of the study show the effect of diversification in both the degree and the types (not diversified, related, unrelated and combined) on business performance Secondly, The research indicates both the direct and the interactive influences of the diversification types, the degree of diversification and the firm size on business performance The unrelated diversification negatively affects the business performance, however, this negative influence is weaken as the firm size increases or when it is combined with the related diversification In particular, this negative influence will decrease as the firm size increases from small to medium and from medium to large On the other hand, the combination of related and unrelated diversification has a positive effect on business performance Thirdly, The study also shows that there is no difference in the effect of diversification on business performance between the commercial-service sector and production firms (although the degree of diversification on average of these two groups is different) New recommendations as the results of the research Firstly, The research results provide implications for firms to make decisions that govern the expansion or reduction of their business scope according to the size and the actual situation of the types of business diversification Secondly, The cohesion between the business areas of the company enhances the ability to share resources and transfer skills to take advantage of both the economies of scale and of scope So far, study results suggest that company should prioritise the related diversification first, then implement the unrelated diversification to achieve the balance between the development objective and the business performance objective Thirdly, The typical cases study of commercial-services and manufacturers sector can help companies making practical solutions in the implementation of diversification in Vietnam Accordingly, development of focused specialization and diversification in moderation level should be the basic strategy for most Vietnam enterprises in long term Enterprises should only expand diversified business lines when they already have built their core competencies in their main business areas Supervisors Assoc Prof Dr Tran Van Bao Ph.D Candidate Dr Nguyen Minh Ngoc Pham Thi Thanh Huong