In this thesis work, a new technique for designing logic circuits called the Modified Gate Diffusion Input (MGDI) logic is discussed. This logic is adopted from the Gate Diffusion Input (GDI) technique. GDI was first proposed in the year 2002 for solving the problems associated with different CMOS logic styles. GDI cell can be used to implement wide variety of complex logic functions using only two transistors. GDI technique allows design of high speed and low power circuits with reduced number of transistors as compared to static CMOS and Pass Transistor Logic (PTL) techniques. This work aims to design a various high performance adders and multipliers.