In this work results of the threshold operation of antimonide-based vertical-cavity surface-emitting laser have been presented with the aid of the comprehensive fully self-consistent optical-electrical-thermal-recombination numerical model. Calculations have been carried out for the structure emitting at 2.6 μm. The advantages of incorporating the tunnel junction for current confinement have been shown and the influence of a layer shift caused by presence of the tunnel junction on the mode selectivity has been examined. It was shown that reducing the layer shift, with initial height equal to 55 nm, by the 35 nm leads to 7 and 25 times higher mode losses for LP₁₁ and LP₂₁ modes, respectively, and only 10% higher threshold current for the LP₀₁ mode. Further reduction of the layer shift leads to high increment of the threshold current value: 20% for 40 nm reduction and 50% for 45 nm one.