Little attention has been given to an adverbial as a category in the linguistic handbooks describing Croatian language when compared with other parts of a sentence. As a result, most of them dedicate merely several pages to this category. Spatial adverbial, similarly to other adverbial types, has not been the subject of a larger number of studies even though the prepositional phrases, nominal phrases and adverb expressions, which describe spatial relations, have been the subject of studies in Croatistics and wider linguistic literature. Therefore, this paper aims to place spatial adverbial within a larger theoretical framework of the research and to offer a monograph outline of the category. Starting from theoretical postulates of cognitive linguistics, this doctoral dissertation deals with spatial adverbial within the structure of a simple sentence. Adverbial is a complex category with a large number of fringe examples which are more or less apart from core meaning of this facultative syntactic element, whose placement in a sentence is created by the predicate, and which is inserted purely according to the semantic criterion, so that its omission does not affect the authenticity of the sentence. Therefore, this dissertation attempts to emphasize the range of the spatial adverbial category and the diversity of its roles within a simple sentence, as well as the importance of its role in building up the meaning of a simple sentence. The goals of the study are: expanding the definition of spatial adverbial, the understanding and analysis of which involve a wider context and our knowledge of the world, determining spatial adverbial subcategories and describing the syntactic and semantic characteristics of a certain group with emphasis on various extensions of the meaning within each category. Within the spatial adverbial category it is necessary to distinguish different kinds of adverbials which differentiate more or less in syntactic/grammatical and semantic/meaning characteristics, making it a rule rather than an exception for the same adverbial to be interpreted and categorized differently in different sentences. This dissertation gives a short overview of theoretical approaches to adverbials, particularly to spatial adverbial so as to determine the problems of its definition and the placement in a simple sentence. It also outlines the basic theoretical statements on which the description of adverbials is based. Furthermore, adverbials are being analysed as a part of dynamic and static scenarios (schemes) in which additional explanations are recquired because they function as participants of an occurence whose background framework is being analysed. The particularities of individual prepositional phrases as adverbials are shown in relation to their placement in a sentence, to the possibility of contextualization to lesser or greater degree, different meaning extensions, connection to certain semantic verb groups, the (im)possibility of prefix verbs. Complex concepts such as causality, permission and condition are also being discussed, as well as the meaning expansions of spatial adverbials into those domains. The conclusion of the study brings up certain questions which exceed the framework of this dissertation and could be a subject to possible further studies about the process of grammaticalization, adverbials and subordinate clauses. Literature and used sources are listed at the end of the work.