Bosnia and Herzegovina has a total sea surface area of 8 km2 (http://www.mvteo.gov.ba) with a maximum depth of 27 m. The country has only 24.5 kilometers (15 mi) of coastline around the town of Neum which is the only coastal town in Bosnia and Herzegovina and an important tourism destination. Taxonomic and ecological studies of marine diatoms have been started, for the first time ever, in Bosnia and Herzegovina at the beginning of 2010. According to our preliminary data, 116 marine diatom taxa (both benthic and planktonic) within 51 genera have been found in the country. The aim of this study was to determine the colonization processes of diatoms on the surface of the glass substrate. For this purpose, samples were taken from the glass slides at 1 m depth during spring and summer 2011. Periphyton was sampled each two weeks during both seasons. Additionally, samples for physical-chemical parameters were taken to determine environment- diatom relationships.