Two constructions of microfluidic structures are described in this paper. A fibre optic microcell for spectrophometric measurements and a microcell for fluorescence experiments were designed and tested. The structures were made of polymer optical fibres which were incorporated into polymeric material i.e. poly(dimethylsiloxane). The structures were tested as detectors in absorbance measurement (solutions of bromothymol blue with diffierent pH were used) and in fluorescence tests (solution of fluoresceine was used).