The invention discloses a method and an apparatus for determining the condition or genuineness of flat articles, in particular bank-notes. The bank-note passes through a test station in which a large portion of its surface is scanned by a scanning system as it passes through. The electric signals generated by the scanning system are edited in an analyzing electronic circuit and compared with suitable limiting values and a signal denoting a faulty position is generated when a certain tolerance is exceeded. At least one surface portion defined in respect of position and size is selected and the electric signals appropriate to the scanning of this surface portion are compared only with limiting values selected for this portion. Thus, it is possible to check the condition and/or genuineness of flat articles, such as sheets of paper, securities, bank-notes and the like while the general rate of rejection and the exact analysis of preferred portions can be equally set alongside one another, without influencing one another, and examined.