This study aims to discuss the noun and prepositional phrases in English and in Vietnamese and their impact upon teaching and learning English in the Vietnamese situation. Attempts have been made to state the similarities and differences in noun and prepositional phrases in the two languages and raise and solve some difficulties and problems arising particularly from differences between English and Vietnamese. In this study, Contrastive Linguistics is concerned with the comparison of the two languages with a view to determining the differences and similarities between them. With this practical aim the study tries to provide a model for comparison and determine how and which of the phrases are comparable. It is hoped to provide as much information as is possible in a limited study of this kind on English noun and prepositional phrases, then on Vietnamese noun phrases. The study draws attention to differences with examples. It analyses the heads of noun phrases in the two languages as well as the pre and postmodifications and their positions. It also analyses the uses of the prepositional phrases in the two languages. At the same time, it points out the kinds of errors made by Vietnamese learners in the above-mentioned areas and their causes. Finally, some suggestions are made for those who may be responsible for teaching English as a Foreign Language to younger pupils as well as adults, or to students at universities or colleges