Spanwise correlation behavior of both total vertical vortex-induce lift (VIL) and pure vertical vortex-shedding lift (VSL) on a flat closed-box deck under both still and vortex-induced resonance (VIR) states was investigated via a pressure measurement wind tunnel test of spring-suspended sectional model constructed at a large scale of 1/20. The correlation coefficients of VSL on the still deck model and those of total VIL on the deck model under VIR state were calculated directly based on the measured fluctuating lift forces, whilst the correlation coefficients of VSL on the deck model under VIR state were extracted from those of total VIL according to an approximate relationship between the two correlation coefficients established in this study. The results show that the spanwise correlation of total VIL can be greatly intensified by the VIR because of the existence of a large portion of vortex-induced self-excited lift (VISEL) contained in the total VIL. On the other hand, the spanwise correlation of VSL under VIR state is much weaker than that of total VIL as well as that of VSL under still state at same wind speeds. Furthermore, the relationship between the spanwise correlation of VIL or VSL and the VIR response is quite complicated. The most violent VIR, the most correlated VIL and the most correlated VSL are not corresponding to each other.