The dissertation aimed to study compounding and lexical blending in the English and Thai languages in order to examine in a contrastive perspective two sets of nominal compounds and two sets of lexical blends. In the study, the data of both languages were collected manually from dictionaries of new words, leading to four sets of data: (1) 473 Thai compound nouns, (2) 247 English compound nouns, (3) 35 Thai lexical blends (taken from the overall list of 37,104 neologisms), and (4) 100 English lexical blends were collected manually from three different dictionaries. The data were analyzed in order to present two aspects of compound nouns and lexical blends in the Thai and English languages: 1) their formal classification, and 2) their semantic characteristics. Two data sets of compound nouns in Thai and English were analyzed to examine a variety of linguistic features: the number of structures, the semantic types of compounds (e.g., coordinative compounds and subordinative compounds), headedness, and metaphtonymic shifts (i.e., the different degrees of opacification, contrasting literal compounds and figurative compounds). These findings were examined in order to find out the similarities and differences of nominal compounding in the two languages. Two data sets of lexical blends in Thai and English were also analyzed in order to determine various features: the types of lexical output, the types of lexical input combination, the patterns of lexical shortening, the types of segment overlap and phonological splitting, headedness, and metaphtonymic shifts. As for the data sets of nominal compounds, the findings for lexical blends were compared to examine the similarities and differences of lexical blending in the two languages. The findings of the study were summarized as follows: (1) The comparison of nominal compounding in Thai and English shows a number of marked dissimilarities between the two languages. Thai compound nouns can be distinguished from English compound nouns to the extent that they typically display more varied types of patterns, both in terms of number of elements (up to five) and of combination of lexical patterns (using a wider number of non-nouns). Thai compounds can also be characterized by a stronger external influence than is the case for English: they can contain many foreign elements (primarily from Pali and Sanskrit) and adopt patterns that are not displayed natively (like right-head structuring). In spite of their differences, it was found that Thai and English share a number of basic constructions: N-N, N-ADJ, N-ADV, V-N, V-V. Semantically, Thai and English both make use of the two main types of nominal compounding: subordinate compounds and coordinate compounds. Noticeably, the proportions of the different semantic types of compound noun in both languages are remarkably similar: 98% for subordinates and 2% for coordinates; and they also share a very small number of attributive subordinates. The two languages display a salient typological contrast as far as headedness is concerned: the head in a Thai compound is canonically on the left while the head of an English compound noun is on the right. The majority of nominal compounds in both Thai and English are transparent, but the number of semantically figurative compounds in English is higher than in Thai. In the two languages, compounds exist where one member is used figuratively while the other remains literal. Thai has a much higher percentage of compounds with a transparent head and a figurative non-head element, as well as a much higher number of compounds with an opaque head and a transparent non-head element.