In this work, we have studied five different GRBs detected by Swift: GRB 071010B (z = 0.94), GRB 080411 (z = 1.03), GRB 080413B (z = 1.10), GRB 091208B (z = 1.06) and GRB 110715A (z = 0.82); Those GRBs, with similar z and have well defined pulses. To obtain spectral lag, we fit the light curves with a model having exponential rise and decay parts. In addition, we performed spectral analysis using three spectral models for different GRBs' regions: power law, cutoff power law and band model. Additionaly, we releated spectral parameters such as photon index and luminosity with spectral lag. The analysis suggests that there are two types of pulses associated to specific radiation mechanisms which would reveal the radiation process of long gamma-ray bursts.