Automatic behaviour recording using dataloggers attached to the animals is increasingly used in cattle research. Surprisingly there has been only little research on the influence of such devices on the observed behaviour. It was therefore the aim of this study to investigate the effect of differently sized dataloggers or a bandage attached to the metatarsus of dairy cows on different measures of lying behaviour. In total 48 cows were used in two subsequent periods. Animals were housed in free stalls with sand bedding. In each period, six cows each were randomly allocated to one of the following treatments: control, bandage, small logger, large logger. Each experimental period lasted for ten days with switching the side of attachment after five days. Lying behaviour was continuously recorded using video cameras for in total eight days; additionally, direct observations were carried out on two days. GLM was used to analyse the effect of treatment and side of attachment as well as the interaction between treatment and side of attachment on different measures of lying behaviour. No significant treatment or interaction effects were found for lying time, number of lying bouts, average duration of lying bouts and the proportion of different lying positions. However, the presence of a logger/bandage significantly reduced lying time on the left side when it was attached to the left hind leg as compared to the right leg (p=0.047). It is concluded that the dataloggers used in this study do not generally influence the lying behaviour of dairy cattle under similar housing conditions. Less comfortable housing conditions (e.g. slatted flooring for beef cattle, hard rubber mats in free stalls or other less compressible surfaces in the lying area) may however provoke more pronounced effects due to material and shape of the dataloggers. For future studies aiming at the investigation of the lying side, it is recommended to randomly attach the dataloggers to both hind legs.