This study aimed to verify the influence of silicon application in hydroponics lettuce cv Lucy Brown, on post-harvest under refrigeration. In hydroponic production silicon was used in the doses of 0, 28, 56 and 84 mg L -1 of potassium silicate. Lettuces were harvested early in the morning and immediately transported to UNESP, campus of Jaboticabal. Upon being received at the laboratory the plants were standardized in size and appearance, removing the three older leaves. The plants were placed in polystyrene trays (Styrofoam © ) and packaged under the temperature at 8±2°C and 80 ± 3% relative humidity. The experimental design was completely randomized with three replications, and two plants per repetition. The fresh matter of shoots was analyzed together with the silicon content in the leaves, the firmness, the fresh matter loss, titratable acidity, pH and enzyme activity of polyphenoloxidize and peroxides. The evaluations were performed every four days, for a total of 16 days of storage. The concentration of 84 mg L -1 silicon increased the fresh matter of the plant at harvest and post-harvest, provided less water loss and consequently greater firmness in the leaves during the storage period for lettuce at 8±2°C for 16 days.