The Collaborative International Dictionary of English v.0.48:

Smallness \Small"ness\, n.
   The quality or state of being small.
   [1913 Webster]

WordNet (r) 3.0 (2006):

smallness
    n 1: the property of having a relatively small size [syn:
         smallness, littleness] [ant: bigness, largeness]
    2: the property of being a relatively small amount; "he was
       attracted by the smallness of the taxes"
    3: the property of having relatively little strength or vigor;
       "the smallness of her voice" [syn: smallness, littleness]
    4: lack of generosity in trifling matters [syn: pettiness,
       littleness, smallness]

Moby Thesaurus II by Grady Ward, 1.0:

158 Moby Thesaurus words for "smallness":
   Lenten fare, abjectness, abominableness, atrociousness, austerity,
   authoritarianism, baseness, beggarliness, bigotry, blind side,
   blind spot, blinders, chinchiness, chintziness, closed mind,
   contemptibility, contemptibleness, cramped ideas, crumminess,
   debasement, deficiency, degradation, depravity, despicableness,
   diminutiveness, enormity, execrableness, exiguity, exiguousness,
   failure, fanaticism, fewness, foulness, fulsomeness, grossness,
   heinousness, hideboundness, homeliness, humbleness, humility,
   illiberality, immateriality, imperfection, inadequacy,
   incompetence, inconsequence, inconsequentiality,
   inconsiderableness, indifference, ineffectuality, inferiority,
   infrequency, ingloriousness, innocuousness, insignificance,
   insufficiency, insularism, insularity, irrelevance, jejuneness,
   jejunity, leanness, little-mindedness, littleness, low priority,
   lowlihood, lowliness, lowness, maladroitness, marginality,
   meagerness, mean mind, meanness, mediocrity, meekness, minginess,
   minuteness, miserableness, miserliness, modesty, monstrousness,
   narrow sympathies, narrow views, narrow-mindedness, narrowness,
   nearsightedness, nefariousness, negligibility, niggardliness,
   obnoxiousness, odiousness, odium theologicum, paltriness,
   parochialism, parsimony, paucity, pettiness, petty mind, picayune,
   picayunishness, plainness, pokiness, poorness, provincialism,
   puniness, purblindness, rankness, rarity, restrictedness,
   scabbiness, scantiness, scantness, scarcity, scrawniness,
   scrimpiness, scrubbiness, scruffiness, scumminess, scurviness,
   secondariness, shabbiness, shoddiness, shortness, shortsightedness,
   shut mind, simpleness, skimpiness, slenderness, slightness,
   slim pickings, slimness, spareness, sparseness, sparsity, squalor,
   stinginess, straitlacedness, stringency, stuffiness,
   submissiveness, subnormality, teachableness, thinness, tightness,
   tininess, triviality, uncatholicity, undersize, ungenerousness,
   unimportance, unimpressiveness, unmagnanimousness,
   unnoteworthiness, unpretentiousness, unskillfulness, vileness,
   vulgarity, wretchedness