In the present paper, the effect of a centrally placed circular obstruction on sloshing frequency and sloshing mass is studied for annular tanks. Finite element approach (ANSYS software) is used to model the liquid. For circular tanks without obstruction, sloshing frequency and sloshing mass at first three modes are obtained using finite element analysis which compare well with the available analytical results. Next, a rigid circular obstruction at the center of tank is modeled and sloshing frequency and modal mass in the first three modes are obtained. It is observed that with the increase in the diameter of the circular obstruction, the sloshing frequency and the percentage of liquid in sloshing mode decrease in first mode. The behavior of these sloshing parameters in higher modes is also discussed. A detailed study over wide range of circular tank geometries is performed. Charts for obtaining sloshing parameters for various tank geometries are plotted.