Liquefied natural gas (LNG) tanks are considered essential structures. Storage tanks in particular, are important to the continued operation of natural gas distribution systems in the event of earthquakes. The Finite Element (FE) method is utilized to model the tank, as well as the contained fluid. ANSYS 12, a finite element code that combines structural and fluid simulation capabilities, has been used to model the inner steel tank, LNG fluid, and outer concrete tank in the three-dimensional space and perform modal and nonlinear seismic analysis. The tank wall is modelled by shell elements. The LNG has been represented as contained fluid elements. In this paper, the analysis results for mode shapes and natural frequencies obtained by ANSYS 12 are compared with those calculated by theoretical calculations using the guidelines for seismic design of liquid storage tanks presented by Indian Institute of Technology -2007. The results obtained for the fundamental frequency and mode shapes gave basic knowledge and better understanding of LNG tanks in dynamic analysis.