The motion of drops suspended in another fluid has a wide variety of practical applications. These include the flow of oil and water through pipelines, the recovery of oil through porous rock, the flow of slurries and polymer processing. The lateral migration of deformable particles in Poisseuile flow has been subject of many investigations. The lateral migrations of immersed objects in carrier fluids are very important in traort processes, where mass, momentum and energy are exchanged. The lateral migration of a drop in Poisseuile flow is studied numerically in two dimensions . The mechanism of lateral migration for one drop was explained by Feng et al. The wall repulsion force which is known as a lubrication effect drives the drop to the channel centerline. A Magnus type lift force acts on the drop which depends on drop rotation and drop slip velocity. The direction of this lift depends on whether the drop leads or lags the flow. The curvature of velocity profile also imposes a lateral force that always drives the drop to the channel walls. Besides, the inertia of flow develops a lateral force which is known as inertia lift (Saffman lift) that depends on the direction of the slip velocity. The equilibrium position of a drop is a result of balance between aforementioned forces. In this research the lateral migration of two-dimensional drops with two different sizes in Poiseuille flow at finite Reynolds numbers are studied numerically under conditions of negligible gravitational force. The full Navier-Stokes equations are solved by a finite difference/front tracking method that allows a fully deformable interface between the drop and the suspending medium. The effect of dimensionless parameters on the effective viscosity , the fluctuation energy across the channel and particle size segregation are investigated. Simulations were performed at a unity density and viscosity ratio with a constant areal fraction ( ). The number of drops considered were 24, 48 and 51 that were suspended inside a periodic channel using two different initial configurations. Results show that the average density distribution of drops across the channel are independent of the initial configuration. The density distribution of large and small drops are different. Therefore a particle size segregation is observed. There is a tendency for large drops to migrate to the center of the channel, whereas small drops migrate towards the channel walls. The effect weakens as the Reynolds number increases and Capillary number decreases. Drops segregation also weakens when drop sizes get close (51 drops). The strongest segregation occurs when the difference between drop sizes is largest (24 drops). Keywords: oisseuile flow, Effective viscosity, Particle size segregation, Density distribution, Different sizes