Recently it has been shown that maleic anhydride (MA) on Si(1 0 0) binds preferentially above the dimer troughs. This has been postulated to arise from the electrophilic nature of MA. We perform density-functional calculations at low and high coverage limit that indicate the importance of long-range substrate relaxations and explain the observed increasing preference for above-trough binding with increasing surface coverage. The electrophilic nature of MA gives rise only to small changes in the binding strength, but these may be large enough to explain the observed binding if kinetic rather than thermodynamic reaction control occurs.