The use of recycled fibre in newsprint production affects the composition of the newsprint. This is due to paper additives, such as fillers and fluorescent whitening agents (FWAs), that are introduced in the newsprint via the recycled fibre. The more or less aged recycled fibres also affect the quality of the paper. This suggests a need of on-line monitoring of the distribution of recycled fibre during production. In this project, portable optical equipment for such inspection has been developed and tested in laboratory environment. The equipment is based on detection of fluorescence principally from FWAs. Ultraviolet light is focused to a small, superficial volume in the paper, and detection of the fluorescence light from the excited volume is made around 450 nm. Tests of the signal response have been performed on paper samples containing different amounts of recycled fibre and other substances. The equipment has also been tested on a running web in the laboratory, demonstrating the possibilities of performing well-resolved, fast on-line measurements.