Purpose - This paper aims to study the packing density of printed paths on different substrate materials. It presents problems which appear when the necessity of printing one or more narrow paths occurs. Design/methodology/approach - A piezoelectric printhead containing nozzles with a diameter of 35 mm was used for printing nanoparticle silver ink on different polymer substrates which were treated by plasma or not treated at all. The shape, defects, resistance and printing parameters for the printed paths were analysed. Findings - The obtained results allow the identification of the sources of the technological problems in obtaining a high packing density of the paths in a small area of substrate and the repeatable prints. Research limitations/implications - The study could have limited universality because of the chosen research method; printhead, ink, substrate materials and process parameters were arbitrarily selected. The authors encourage the study of other kinds of conductive inks, treatment methods and printing process parameters. Practical implications - The study includes practically useful information about widths, shapes, defects and the resistance of the paths printed using different technological parameters. Originality/value - The study presents the results of original empirical research on problems of the packing density of inkjet printed paths on a small area of substrate and identifies problems that must be resolved to obtain effective interconnections in the inkjet technology.