A metallic carbon nanotube with point-like defects under influence of a local potential due to a point charge probe is theoretically studied. A combination of density functional theory and the Landauer-Buttiker formalism is used to compute the electronic conductance in the zero-voltage limit. From a collection of the results obtained by varying the probe position around different defects the conductance maps are created. The analysis of the conductance maps allows us to formulate conditions under which several point-like defects (the Stone-Wales defect, a simple carbon vacancy, hydrogen-passivated vacancies) can be distinguished and identified in experiments with the help of scanning probe microscopy. (C) 2015 Elsevier B.V. All rights reserved.