One of the items of Sewerage and Drainage System Improvement Project in Hanoi - phase I is to dredge and conserve 5 lakes: Thien Quang, Thanh Cong, Giang Vo, Thanh Nhan 1 and Thanh Nhan 2. In 2005, Center for Environmental Engineering of Towns and Industrial Areas (CEETIA) carried-out the scientific research work No 01C-09/06-2005-1. The purposes of the work are to assess the existing situation and to predict a change of water quality in the lakes. Considering the results of the water quality monitoring the authors propose a suitable technical measures for conservation of the remains of urban lakes and for water quality improvement of the rehabilitated lakes.