The traditional methodology assumes independence between competing failure modes to estimate the reliability function, but recent studies have shown that when this assumption is incorrectly assumed, usually gives pessimistic estimates. This paper intends, through a simulation study, to explore the effect caused by such a situation in the cases of two competing lognormal failures and two competing Weibull failures. It is appreciated from the results that, when the dependence is ignored, there are no significant differences between the true reliability function and the estimated reliability function assuming independence.