AbstractCurrently the only technique sensitive to Earth mass planets around nearby stars (that are too close for microlensing) is the monitoring of the transit time variations of the transiting extrasolar planets. We search for additional planets in the systems of the hot-Neptune GJ-436 b, and the hot-Jupiter XO-1 b, using high cadence observations in the J and K_S bands, with the SofI and ISAAC instruments from La Silla Paranal Observatory. New high-precision transit timing measurements were used to derive new ephemeris. No statistically significant timing deviations were detected. We demonstrate that the high cadence ground based near-infrared observations are successful in constraining the mean transit time to 30 sec, and are a viable alternative to space missions.