This thesis will present empirical evidence on the spatial meanings of the Croatian prepositions ‘na’ and ‘u’ and compare them to their English equivalents, as well as relate the findings to the existing body of research. A total of 32 items was chosen chosen from the BowPed picture series in order to analyse spatial expressions (predominantly prepositions) used to encode various types of static topological relations. The participants who took part in the study (31 NSs of Croatian) were asked to locate the objects shown in the pictures both in Croatian and in English. Their answers were mostly obtained via Zoom video calls, as the primary focus of the study was natural, spoken interaction. The descriptions of the items provided by the participants are discussed in the context of the ‘on-in continuum’ designed by Bowerman and Pederson. The results seem to point to different cut-off points (i.e. boundaries) between categories of spatial relations in Croatian when compared to the English mode of spatial conceptualisation. Additionally, it has been found that two of the categories might be reversed in the minds of Croatian speakers. The most significant differences are observed with regard to the following categories: TRs impaled/spitted on LMs, encirclement with contact (a potential reversal of the categories), gaps or objects embedded in physical objects and relations of partial inclusion (closer to ‘na’ in Croatian and ‘in’ in English). Moreover, a part of the analysis is dedicated to verbs that sometimes occurred in the descriptions. This particular section of the thesis also explores the repetitive pattern typically found in some Slavic languages consisting of a prefixed verb followed by a preposition which is a cognate of the prefix. It was found that these repetitive structures (as well as verbs in general) were predominantly used when the participants felt the need to further specify a relation, or when they interpreted the picture as dynamic. Finally, the study was aimed at establishing whether L2 proficiency plays an important role in the lexicalisation of static spatial relations in English. The participants were divided into two groups based on their level of proficiency (independent (A2-B1) and proficient (C1-C2) speakers). After comparing their English descriptions of the selected items, it was concluded that 1) speakers in both groups showed a tendency to ‘switch’ to more native-like descriptions (the saliency of support decreased, whereas the saliency of containment increased in the English descriptions), and 2) that the more proficient group consistently showed higher awareness of the differences between Croatian and English modes of spatial conceptualisation. Due to the small number of participants, the results could not be discussed in terms of statistical significance, but they do seem to suggest that proficiency has at least some influence on the encoding of static spatial relations in L2.