WFCAM JHK colour–colour diagram of a 2′ × 2′ region surrounding IRAS 18345; UKIDSS data obtained in better sky conditions are used. The blue dots show the colours of point sources detected. The red dots are the colours of sources “A” and “B” derived from the most recent observations. The continuous green lines show the colours of unreddened main sequence and red-giant stars taken from Tokunaga et al. (2000). The long-dashed green line shows the loci of CTTS from Meyer et al. (1997). The long red arrows show the reddening vectors for A_V ≤ 50 derived from the interstellar extinction law given by Rieke & Lebofsky (1985).