Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress calculations are based on the Irving-Kirkwood method, which divides the stress tensor into its kinetic and virial parts. The kinetic component recovers pressure based on the ideal gas law. The particle-particle virial increases with increased density, while the surface-particle virial develops due to the surface force field effects. Normal stresses within nano-scale confinements show anisotropy induced primarily by the surface forcefield and local variations in the fluid density near the surfaces. For dilute and dense gas cases, surface-force field that extends typically lnm from each wall induces anisotropic normal stress. For liquid case, this effect is further amplified by the density fluctuations that extend beyond the force field penetration region. Outside the wall force-field penetration and density fluctuation regions the normal stress becomes isotropic and recovers the thermodynamic pressure, provided that sufficiently large force cutoff distances are utilized in the computations. Next, non-equilibrium SWMD is utilized to investigate the surface-gas interaction effects on nanoscale shear-driven gas flows in the transition and free molecular flow regimes. For the specified surface properties and gassurface pair interactions, density and stress profiles exhibit a universal behavior inside the NOMENCLATURE English Symbols a Acceleration, nm/ns 2 Cm Mean thermal speed, nm/ns fu Force acting on molecule i from molecule j, N F Force, N H Channel height, nm k Modified Knudsen number, (No Units) h Boltzmann constant, (J K" 1) Kn Knudsen number, (No Units) L Channel length, nm m Mass, kg M Mach number, (No Units) N Number of molecules, # P Momentum P Pressure, kPa Q Mass parameter, (No Units) r ij Spacing between the molecules i and j, nm r c CutofF distance, nm R Specific gas constant, J K" 1 kg" 1 Re Reynolds number, (No Units) s Steps, (No Units