Abstract <p>The article discusses the longitudinal tension of two-layered plates of orthorhombic crystals. Expressions for effective Young’s moduli and Poisson’s ratios for different loading directions are obtained. With use of available experimental data on the elasticity constants, variability of effective elastic properties of plates is analyzed for all possible combinations of orthorhombic crystals. Plates with effective Young’s modulus greater than Young’s moduli of the layers and plates with a negative effective Poisson’s ratio are identified.</p>