Identifying defects in marginally failed vias has long been a challenge for failure analysis (FA) of state-of-the-art semiconductor integrated circuits. This paper presents two cases where a conventional FA approach is found to not be effective. The first case involves high resistance or marginally open vias. The second case involves early breakdown of large capacitors. The large size of the capacitor and the lack of ways to track electrical flow during diagnosis made it difficult to isolate the defect. The paper shows that conducting atomic force microscopy (C-AFM) and scanning capacitance microscopy (SCM) are effective techniques for isolation of via-related defects. The SCM technique could be applied to samples without a direct conducting path to the substrate, such as SOI samples. On the other hand, C-AFM allows current imaging as well as I-V characterization whenever a direct conductive path is available.