A system for transcranial stimulation of a head region of a subject, wherein the system includes an electrode arrangement comprising a plurality of electrodes coupled to at least one electrode drive arrangement, wherein the plurality of electrodes are operable to contact onto a scalp of the head region of the subject, wherein the at least one drive arrangement is operable to generate electrical signals for driving the plurality of electrodes to cause transcranial stimulation of the head region of the subject, wherein the system includes a monitoring arrangement for monitoring spatial positions of the plurality of electrodes relative to the head region of the subject and/or mutual relative positions of the plurality of electrodes, and for indicating positional errors of the one or more electrodes for enabling repositioning of the plurality of electrodes and/or a change in the electrical signals applied to the plurality of electrodes, for providing improved transcranial stimulation of the head region of the subject; wherein the electrode arrangement includes features which enable spatial positions of the plurality of electrodes relative to the head region to be measured using a sensing arrangement of the monitoring arrangement, wherein the sensing arrangement is coupled to computing hardware of the monitoring arrangement for computing the positional errors of the one or more electrodes; characterized in that the sensing arrangement is implemented, at least in part, using a mobile wireless communication device equipped with at least one imaging sensor for imaging the features for generating at least one image signal for the computing hardware for use in computing the positional errors, wherein the features include at least one of: (i) one or more light sources which are individually excitable for indicating the spatial positions of their respective electrodes relative to the head region of the subject; and (ii) figures with a combination of colours. the system includes a monitoring arrangement for monitoring spatial positions of the plurality of electrodes relative to the head region of the subject and/or mutual relative positions of the plurality of electrodes, and for indicating positional errors of the one or more electrodes for enabling repositioning of the plurality of electrodes and/or a change in the electrical signals applied to the plurality of electrodes, for providing improved transcranial stimulation of the head region of the subject; wherein the electrode arrangement includes features which enable spatial positions of the plurality of electrodes relative to the head region to be measured using a sensing arrangement of the monitoring arrangement, wherein the sensing arrangement is coupled to computing hardware of the monitoring arrangement for computing the positional errors of the one or more electrodes; characterized in that the sensing arrangement is implemented, at least in part, using a mobile wireless communication device equipped with at least one imaging sensor for imaging the features for generating at least one image signal for the computing hardware for use in computing the positional errors, wherein the features include at least one of: (i) one or more light sources which are individually excitable for indicating the spatial positions of their respective electrodes relative to the head region of the subject; and (ii) figures with a combination of colours. (i) one or more light sources which are individually excitable for indicating the spatial positions of their respective electrodes relative to the head region of the subject; and (ii) figures with a combination of colours. <EOS>