Compn. of dry and wet-weather inflows of wastewater to the Lodz wastewater treatment plant (WTP) in 2003-2007 were analyzed for contents of suspensions, P and ammonium N as well as COD and total Kjeldahl N. The changes of the parameters during storming weather (June 13, 2007) and intensive snowmelt event (March 16-19, 2005) and their effect on the operation of WTP were presented and discussed. The increased wastewater intensity was accompanied by a decreased COD and concn. of ammonium N but also with an increased content of suspensions in the WTP inlet stream were considerably increased. The concn. of suspensions in the WTP inlet stream was found a crit. parameter of the WTP operation.