-The effect of defects on the behaviour of electrical conductivity, σ, in a monolayer produced by the random sequential adsorption of linear k-mers (particles occupying k adjacent sites) onto a square lattice is studied by means of a Monte Carlo simulation. The k-mers are deposited on the substrate until a jamming state is reached, i.e. a state where no one additional particle can be placed because the presented voids are too small or of inappropriate shapes. The presence of defects in the lattice (impurities) and of defects in the k-mers with concentrations of d l and d k , respectively, is assumed. The defects in the lattice are distributed randomly before deposition and these lattice sites are forbidden for the deposition of k-mers. The defects of the k-mers are distributed randomly on the deposited k-mers. The sites filled with k-mers have high electrical conductivity, σ k , whereas the empty sites, and the sites filled by either types of defect have a low electrical conductivity, σ l , i.e., a high-contrast, σ k /σ l ≫ 1, is assumed. We examined isotropic (both the possible x and y orientations of a particle are equiprobable) and anisotropic (all particles are aligned along one given direction, y) deposition. To calculate the effective electrical conductivity, the monolayer was presented as a random resistor network (RRN) and the FrankLobb algorithm was used. The effects of the concentrations of defects d l and d k on the electrical conductivity for the values of k = 2 n , where n = 1, 2, . . . , 5, were studied. Increase of both the d l and d k parameters values resulted in decreases in the value of σ and the suppression of percolation. Moreover, for anisotropic deposition the electrical conductivity along the y direction was noticeably larger than in the perpendicular direction, x. Phase diagrams in the (d l , d k )-plane for different values of k were obtained.