Electronic Speckle Pattern Interferometry (ESPI), a non-contact and non-destructive optical techniques, was employed for assessing the conservation state of a XVI Century painting on wood (72x88x1,9 cm). By a long term analysis, the whole structure alterations, induced by the room temperature and relative humidity variations, were evaluated. Measurement of the whole painting structural bends was achieved. Local flaws and hidden detachments of pictorial layers from the support, which cannot be recognized by traditional art-restorer methods, were also revealed. This work was prevalently aimed at achieving a simple approach, in the laboratory practice, to get an intuitively user-friendly method for art conservators, not accustomed to high-tech or math based methods. The results demonstrate that ESPI can largely improve the traditional art conservation survey techniques.