The paper presents the assessment of reliability depending on the reinforcement cover thickness for elements subject to bending. Based on the experimental tests of 12 reinforced concrete beams subjected to four-point bending the numerical model was validated. In the next steps this numerical model was used for the Monte Carlo simulation. During the analyses the failure probability and the reliability index were determined by two methods – using probabilistic method –FORMand fully probabilistic method Monte Carlo with the use of variance reduction techniques by Latin hypercube sampling (LHS). The random character of input data – compressive strength of concrete, yield strength of steel and effective depth of reinforcement were assumed in the analysis. Non-parametric Spearman rank correlation method was used to estimate the statistical relationship between random variables. Analyses have shown a significant influence of the random character of effective depth on reliability index and the failure probability of bending elements.