Lawnmowers smoke normally if the oil is overfilled, when first starting after choking or priming, or when mowing on a slope.
White smoke indicates the engine is burning a small amount of oil. Blue smoke is a larger amount of oil. Black smoke is caused from excessive fuel, running too rich.
Air cooled engines can burn 1/2 ounce of oil per hour and be normal.
If you need more definite information, send another email and include the model number of the engine or lawn mower. Also send some details of how much the lawnmower smokes, how often or when it smokes, and anything you have checked or done to the lawnmower.