This short study aims to analyze the interference (and its negative effects in the daily use of normal Spanish and Portuguese vocabulary) of terms or phrases called, academically and elsewhere, ‘false friends’. This expression entails also a sum of co-lateral effects, resulting from their strong interdependence, at three levels (semantically, stylistically and structurally). Accessorily, in this group, it is also possible to refer to other types of interference, like ‘civilization’ or ‘cultural’. This theme, emerging now at languages didactics, wishes to appeal to a greater attention to the existing communication between Iberian speakers. The Spanish/Portuguese case seems to show a real problem, capable of creating undesirable effects in the general understanding among people. We live and act in this era of global communication, whether we like it or not, mainly thanks to television and Internet, and this problem seems to have now double importance.