In this paper we face system dynamics modelling and cellular automata to model panic processes. We compare both models using phase plans. The results of simulation confirm our hypotheses: First, a collective behaviour is not the arithmetical sum of the individual behaviours. Secondly the crowd causes the emergence of collective panic from individual panic. Both types of methodology produce the emergence of panic and identical curves for different values of initial conditions and parameters. But the effects of thresholds vary according to these values.