The paper deals with failure analysis of hydraulic systems used in mining machines-elements of mechanical systems used for copper ore transportation in underground mine. These machines are: drilling rigs, bolting rigs, dump trucks and loaders. Based on materials obtained from Maintenance Department some basic analyses were done. First, the number of failures with respects to elements of hydraulic systems has been estimated. Next, the probability of failure appearance has been estimated with respect to particular component of hydraulic system and failure analysis has been done for selected group of objects taking into account number of working hours (lifetime) until the first failure and type of failure. Finally, direction of further work has been defined. The next step is quantitative estimation of main sources of failures (so called root cause analysis), it is a present task investigated by the authors.