Abstract. The 3D structure of the inner Small Magellanic Cloud (SMC) is investigated using the red clump (RC) stars and the RRLyrae stars (RRLS), which represent the intermediate-age and old stellar populations of a galaxy. The V and I bands photometric data of the Optical Gravitational Lensing Experiment (OGLE III) catalog is used for our study. The mean dereddened I magnitude of both the RRLS and RC stars are used to study the relative positions of the different regions in the SMC with respect to the mean SMC distance. This shows that the north eastern part of the SMC is closer to us. The line of sight depth of the sub-regions in the SMC are estimated from the dispersions in the mean I$_0$ magnitudes of both the RC stars and the RRLS. A large line-of-sight depth (front to back distance) is obtained from the analysis of both the populations. The similarity in their depth distribution suggest that both these populations occupy a similar volume of the SMC. From these above results the SMC is approximated as a triaxial ellipsoid in which both the RC stars and RRLS are distributed. The parameters of the ellipsoid are obtained using the inertia tensor analysis. An axes ratio of 1:1.3:6.2 with a 1 degree inclination of the longest axis with the line-of-sight is obtained from the analysis of RRLS. The position angle of the projection of the ellipsoid on the sky obtained is 74.5 degrees. The analysis of the RC stars with the assumption that they are extended up to a depth of 2.5 sigma, provided an axes ratio of 1:1.48:6.8 with the longest axis inclined with an angle of 1.3 degree with the line-of-sight. The position angle of the projection of the ellipsoid on the sky obtained is 55.3. The axes ratio and the inclination values match well for both the populations. The possible reasons for the difference in the position angle is discussed. The implications of this study are also discussed.